Pion generalized parton distributions within a fully covariant constituent quark model
Energy Technology Data Exchange (ETDEWEB)
Fanelli, Cristiano [Massachusetts Institute of Technology, Cambridge, MA (United States). Lab. for Nuclear Science; Pace, Emanuele [' ' Tor Vergata' ' Univ., Rome (Italy). Physics Dept.; INFN Sezione di TorVergata, Rome (Italy); Romanelli, Giovanni [Rutherford-Appleton Laboratory, Didcot (United Kingdom). STFC; Salme, Giovanni [Istituto Nazionale di Fisica Nucleare, Rome (Italy); Salmistraro, Marco [Rome La Sapienza Univ. (Italy). Physics Dept.; I.I.S. G. De Sanctis, Rome (Italy)
2016-05-15
We extend the investigation of the generalized parton distribution for a charged pion within a fully covariant constituent quark model, in two respects: (1) calculating the tensor distribution and (2) adding the treatment of the evolution, needed for achieving a meaningful comparison with both the experimental parton distribution and the lattice evaluation of the so-called generalized form factors. Distinct features of our phenomenological covariant quark model are: (1) a 4D Ansatz for the pion Bethe-Salpeter amplitude, to be used in the Mandelstam formula for matrix elements of the relevant current operators, and (2) only two parameters, namely a quark mass assumed to be m{sub q} = 220 MeV and a free parameter fixed through the value of the pion decay constant. The possibility of increasing the dynamical content of our covariant constituent quark model is briefly discussed in the context of the Nakanishi integral representation of the Bethe-Salpeter amplitude. (orig.)
Relativistic Covariance and Quark-Diquark Wave Functions
Dillig, M
2006-01-01
We derive covariant wave functions for hadrons composed of two constituents for arbitrary Lorentz boosts. Focussing explicitly on baryons as quark-diquark systems, we reduce their manifestly covariant Bethe-Salpeter equation to covariant 3-dimensional forms by projecting on the relative quark-diquark energy. Guided by a phenomenological multi gluon exchange representation of covariant confining kernels, we derive explicit solutions for harmonic confinement and for the MIT Bag Model. We briefly sketch implications of breaking the spherical symmetry of the ground state and the transition from the instant form to the light cone via the infinite momentum frame.
Faessler, A; Holstein, Barry R; Lyubovitskij, V E; Nicmorus, D; Pumsa-ard, K; Faessler, Amand; Gutsche, Thomas; Holstein, Barry R.; Lyubovitskij, Valery E.; Nicmorus, Diana; Pumsa-ard, Kem
2006-01-01
We calculate magnetic moments of light baryons and N -> Delta gamma transition characteristics using a manifestly Lorentz covariant chiral quark approach for the study of baryons as bound states of constituent quarks dressed by a cloud of pseudoscalar mesons.
Electromagnetic properties of nucleons and hyperons in a Lorentz covariant quark model
Faessler, A; Holstein, B R; Lyubovitskij, V E; Nicmorus, D; Pumsa-ard, K; Faessler, Amand; Gutsche, Thomas; Holstein, Barry R.; Lyubovitskij, Valery E.; Nicmorus, Diana; Pumsa-ard, Kem
2006-01-01
We calculate magnetic moments of nucleons and hyperons and N -> Delta + gamma transition characteristics using a manifestly Lorentz covariant chiral quark approach for the study of baryons as bound states of constituent quarks dressed by a cloud of pseudoscalar mesons.
Chiral Dynamics of Baryons in a Lorentz Covariant Quark Model
Faessler, A; Lyubovitskij, V E; Pumsa-ard, K; Faessler, Amand; Gutsche, Th.
2006-01-01
We develop a manifestly Lorentz covariant chiral quark model for the study of baryons as bound states of constituent quarks dressed by a cloud of pseudoscalar mesons. The approach is based on a non-linear chirally symmetric Lagrangian, which involves effective degrees of freedom - constituent quarks and the chiral (pseudoscalar meson) fields. In a first step, this Lagrangian can be used to perform a dressing of the constituent quarks by a cloud of light pseudoscalar mesons and other heavy states using the calculational technique of infrared dimensional regularization of loop diagrams. We calculate the dressed transition operators with a proper chiral expansion which are relevant for the interaction of quarks with external fields in the presence of a virtual meson cloud. In a second step, these dressed operators are used to calculate baryon matrix elements. Applications are worked out for the masses of the baryon octet, the meson-nucleon sigma terms, the magnetic moments of the baryon octet, the nucleon charge...
NN Interaction in Chiral Constituent Quark Models
Valcarce, A; González, P
2003-01-01
We review the actual state in the description of the NN interaction by means of chiral constituent quark models. We present a series of relevant features that are nicely explained within the quark model framework.
Nuclear Structure Functions from Constituent Quark Model
Arash, F; Arash, Firooz; Atashbar-Tehrani, Shahin
1999-01-01
We have used the notion of the constituent quark model of nucleon, where a constituent quark carries its own internal structure, and applied it to determine nuclear structure functions ratios. It is found that the description of experimental data require the inclusion of strong shadowing effect for $x<0.01$. Using the idea of vector meson dominance model and other ingredients this effect is calculated in the context of the constituent quark model. It is rather striking that the constituent quark model, used here, gives a good account of the data for a wide range of atomic mass number from A=4 to A=204.
Mesons in the Constituent Quark Model
Institute of Scientific and Technical Information of China (English)
WANG Li; PING Jia-Lun
2007-01-01
The quark-antiquark (q(-q)) spectrum is studied by solving the Schrǒdinger equation in the framework of non-relativistic constituent quark model. An overall good fit to the experimental data of meson is obtained. The interactions between quark and antiquark consist of quadratic colour confinement-exchange, one-gluon-exchange, and Goldstone-boson-exchange potentials.
Quark confinement in a constituent quark model
Energy Technology Data Exchange (ETDEWEB)
Langfeld, K.; Rho, M. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Service de Physique Theorique
1995-07-01
On the level of an effective quark theory, we define confinement by the absence of quark anti-quark thresholds in correlation function. We then propose a confining Nambu-Jona-Lasinio-type model. The confinement is implemented in analogy to Anderson localization in condensed matter systems. We study the model`s phase structure as well as its behavior under extreme conditions, i.e. high temperature and/or high density.
Chiral symmetry and the constituent quark model
Glozman, L Ya
1995-01-01
New results on baryon structure and spectrum developed in collaboration with Dan Riska [1-4] are reported. The main idea is that beyond the chiral symmetry spontaneous breaking scale light and strange baryons should be considered as systems of three constituent quarks with an effective confining interaction and a chiral interaction that is mediated by the octet of Goldstone bosons (pseudoscalar mesons) between the constituent quarks.
Baryons in chiral constituent quark model
Glozman, L Ya
1996-01-01
Beyond the spontaneous chiral symmetry breaking scale light and strange baryons should be considered as systems of three constituent quarks with an effective confining interaction and a flavor-spin chiral interaction that is mediated by the octet of Goldstone bosons (pseudoscalar mesons) between the constituent quarks. One cannot exclude, however, the possibility that this flavor-spin interaction has an appreciable vector- and higher meson exchange component.
Gluonic structure of the constituent quark
Energy Technology Data Exchange (ETDEWEB)
Kochelev, Nikolai, E-mail: kochelev@theor.jinr.ru [Institute of Modern Physics, Chinese Academy of Science, Lanzhou 730000 (China); Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, Dubna, Moscow Region, 141980 (Russian Federation); Lee, Hee-Jung [Department of Physics Education, Chungbuk National University, Cheongju, Chungbuk 361-763 (Korea, Republic of); Zhang, Baiyang; Zhang, Pengming [Institute of Modern Physics, Chinese Academy of Science, Lanzhou 730000 (China)
2016-06-10
Based on both the constituent quark picture and the instanton model for QCD vacuum, we calculate the unpolarized and polarized gluon distributions in the constituent quark and in the nucleon. Our approach consists of the two main steps. At the first step, we calculate the gluon distributions inside the constituent quark generated by the perturbative quark–gluon interaction, the non-perturbative quark–gluon interaction, and the non-perturbative quark–gluon–pion anomalous chromomagnetic interaction. The non-perturbative interactions are related to the existence of the instantons, strong topological fluctuations of gluon fields, in the QCD vacuum. At the second step, the convolution model is applied to derive the gluon distributions in the nucleon. A very important role of the pion field in producing the unpolarized and the polarized gluon distributions in the hadrons is discovered. We discuss a possible solution of the proton spin problem.
Decaying hadrons within constituent-quark models
Kleinhappel, Regina
2012-01-01
Within conventional constituent-quark models hadrons come out as stable bound states of the valence (anti)quarks. Thereby the resonance character of hadronic excitations is completely ignored. A more realistic description of hadron spectra can be achieved by including explicit mesonic degrees of freedom, which couple directly to the constituent quarks. We will present a coupled-channel formalism that describes such hybrid systems in a relativistically invariant way and allows for the decay of excited hadrons. The formalism is based on the point-form of relativistic quantum mechanics. If the confining forces between the (anti)quarks are described by instantaneous interactions it can be formally shown that the mass-eigenvalue problem for a system that consists of dynamical (anti)quarks and mesons reduces to a hadronic eigenvalue problem in which the eigenstates of the pure confinement problem (bare hadrons) are coupled via meson loops. The only point where the quark substructure enters are form factors at the m...
Baryon Wave Functions in Covariant Relativistic Quark Models
Dillig, M
2002-01-01
We derive covariant baryon wave functions for arbitrary Lorentz boosts. Modeling baryons as quark-diquark systems, we reduce their manifestly covariant Bethe-Salpeter equation to a covariant 3-dimensional form by projecting on the relative quark-diquark energy. Guided by a phenomenological multigluon exchange representation of a covariant confining kernel, we derive for practical applications explicit solutions for harmonic confinement and for the MIT Bag Model. We briefly comment on the interplay of boosts and center-of-mass corrections in relativistic quark models.
Double parton distributions in Light-Front constituent quark models
Rinaldi, Matteo; Traini, Marco; Vento, Vicente
2014-01-01
Double parton distribution functions (dPDF), accessible in high energy proton-proton and proton nucleus collisions, encode information on how partons inside a proton are correlated among each other and could represent a tool to explore the 3D proton structure. In recent papers, double parton correlations have been studied in the valence quark region, by means of constituent quark models. This framework allows to understand clearly the dynamical origin of the correlations and to establish which, among the features of the results, are model independent. Recent relevant results, obtained in a relativistic light-front scheme, able to overcome some drawbacks of previous calculations, such as the poor support, will be presented. Peculiar transverse momentum correlations, generated by the correct treatment of the boosts, are obtained. The role of spin correlations will be also shown. In this covariant approach, the symmetries of the dPDFs are unambiguously reproduced. The study of the QCD evolution of the model resu...
Distributions and correlations of constituent quarks in jets
Institute of Scientific and Technical Information of China (English)
黄瑞典; 蔡勖; 钱婉燕; 杨纯斌
2011-01-01
In the frame of the quark recombination model, we study the momentum distributions and correlations of constituent quarks in jets by analyzing the final state hadrons generated by PYTHIA for the hard parton fragmentation processes in vacuum. Parameterizat
Baryons in a chiral constituent quark model
Glozman, L Ya
1998-01-01
In the low-energy regime light and strange baryons should be considered as systems of constituent quarks with confining interaction and a chiral interaction that is mediated by Goldstone bosons as well as by vector and scalar mesons. The flavor-spin structure and sign of the short-range part of the spin-spin force reduces the $SU(6)_{FS}$ symmetry down to $SU(3)_F \\times SU(2)_S$, induces hyperfine splittings and provides correct ordering of the lowest states with positive and negative parity. There is a cancellation of the tensor force from pseudoscalar- and vector-exchanges in baryons. The spin-orbit interactions from $\\rho$-like and $\\omega$-like exchanges also cancel each other in baryons while they produce a big spin-orbit force in NN system. A unified description of light and strange baryon spectra calculated in a semirelativistic framework is presented. It is demonstrated that the same short-range part of spin-spin interaction between the constituent quarks induces a strong short-range repulsion in $NN...
Light baryons in a constituent quark model with chiral dynamics
Glozman, L Ya; Plessas, W
1996-01-01
It is shown from rigorous three-body Faddeev calculations that the masses of all 14 lowest states in the N and \\Delta spectra can be described within a constituent quark model with a Goldstone-boson-exch ange interaction plus linear confinement between the constituent quarks.
Constituent gluons and the static quark potential
Greensite, Jeff
2015-01-01
We suggest that Hamiltonian matrix elements between physical states in QCD might be approximated, in Coulomb gauge, by "lattice-improved" tree diagrams; i.e. tree diagram contributions with dressed ghost, transverse gluon, and Coulomb propagators obtained from lattice simulations. Such matrix elements can be applied to a variational treatment of hadronic states which include constituent gluons. As an illustration and first application of this hybrid approach, we derive a variational estimate of the heavy quark potential for distances up to 2.5 fm. The Coulomb string tension in SU(3) gauge theory is about a factor of four times greater than the asymptotic string tension. In our variational approach, using for simplicity a single variational parameter, we can reduce this overshoot by nearly the factor required. The building blocks of our approach are Coulomb gauge propagators, and in this connection we present new lattice results for the ghost and transverse gluon propagators in position space.
Constituent gluons and the static quark potential
Energy Technology Data Exchange (ETDEWEB)
Greensite, Jeff [San Francisco State Univ., CA (United States); Szczepaniak, Adam P. [Indiana Univ., Bloomington, IN (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
2016-04-01
We suggest that Hamiltonian matrix elements between physical states in QCD might be approximated, in Coulomb gauge, by "lattice-improved" tree diagrams; i.e. tree diagram contributions with dressed ghost, transverse gluon, and Coulomb propagators obtained from lattice simulations. Such matrix elements can be applied to a variational treatment of hadronic states which include constituent gluons. As an illustration and first application of this hybrid approach, we derive a variational estimate of the heavy quark potential for distances up to 2.5 fm. The Coulomb string tension in SU(3) gauge theory is about a factor of four times greater than the asymptotic string tension. In our variational approach, using for simplicity a single variational parameter, we can reduce this overshoot by nearly the factor required. The building blocks of our approach are Coulomb gauge propagators, and in this connection we present new lattice results for the ghost and transverse gluon propagators in position space.
Axial form factors of the octet baryons in a covariant quark model
Ramalho, G
2015-01-01
We study the weak interaction axial form factors of the octet baryons, within the covariant spectator quark model, focusing on the dependence of four-momentum transfer squared, Q^2. In our model the axial form factors G_A(Q^2) (axial-vector form factor) and G_P(Q^2) (induced pseudoscalar form factor), are calculated based on the constituent quark axial form factors and the octet baryon wave functions. The quark axial current is parametrized by the two constituent quark form factors, the axial-vector form factor g_A^q(Q^2), and the induced pseudoscalar form factor g_P^q(Q^2). The baryon wave functions are composed of a dominant S-state and a P-state mixture for the relative angular momentum of the quarks. First, we study in detail the nucleon case. We assume that the quark axial-vector form factor g_A^q(Q^2) has the same function form as that of the quark electromagnetic isovector form factor. The remaining parameters of the model, the P-state mixture and the Q^2-dependence of g_P^q(Q^2), are determined by a f...
Double parton correlations in Light-Front constituent quark models
Directory of Open Access Journals (Sweden)
Rinaldi Matteo
2015-01-01
Full Text Available Double parton distribution functions (dPDF represent a tool to explore the 3D proton structure. They can be measured in high energy proton-proton and proton nucleus collisions and encode information on how partons inside a proton are correlated among each other. dPFDs are studied here in the valence quark region, by means of a constituent quark model, where two particle correlations are present without any additional prescription. This framework allows to understand the dynamical origin of the correlations and to clarify which, among the features of the results, are model independent. Use will be made of a relativistic light-front scheme, able to overcome some drawbacks of the previous calculation. Transverse momentum correlations, due to the exact treatment of the boosts, are predicted and analyzed. The role of spin correlations is also shown. Due to the covariance of the approach, some symmetries of the dPDFs are seen unambigously. For the valence sector, also the study of the QCD evolution of the model results, which can be performed safely thanks to the property of good support, has been also completed.
Distributions and correlations of constituent quarks in jets
Institute of Scientific and Technical Information of China (English)
HUANG Rui-Dian; CAI Xu; QIAN Wan-Yan; YANG Chun-Bin
2011-01-01
In the frame of the quark recombination model, we study the momentum distributions and cor- relations of constituent quarks in jets by analyzing the final state hadrons generated by PYTHIA for the hard parton fragmentation processes in vacuum. Parameterizations for the distributions are tabulated.
Effective Q-Q Interactions in Constituent Quark Models
Glozman, L Ya; Plessas, W; Varga, K; Wagenbrun, R F
1998-01-01
We study the performance of some recent potential models suggested as effective interactions between constituent quarks. In particular, we address constituent quark models for baryons with hybrid Q-Q interactions stemming from one-gluon plus meson exchanges. Upon recalculating two of such models we find them to fail in describing the N and \\Delta spectra. Our calculations are based on accurate solutions of the three-quark systems in both a variational Schrödinger and a rigorous Faddeev approach. It is argued that hybrid {Q-Q} interactions encounter difficulties in describing baryon spectra due to the specific contributions from one-gluon and pion exchanges together. In contrast, a chiral constituent quark model with a Q-Q interaction solely derived from Goldstone-boson exchange is capable of providing a unified description of both the N and \\Delta spectra in good agreement with phenomenology.
Nucleon and gamma N -> Delta lattice form factors in a constituent quark model
Ramalho, G
2008-01-01
A covariant quark model, based both on the spectator formalism and on Vector Meson Dominance, and previously calibrated by the physical data, is here extended to the unphysical region of the lattice data by means of one single extra adjustable parameter - the constituent quark mass in the chiral limit. We calculated the Nucleon (N) and the Gamma N -> Delta form factors in the universe of values for that parameter described by quenched lattice QCD. A qualitative description of the Nucleon and Gamma N -> Delta form factors lattice data is achieved for light pion masses.
Spin Structure Functions in a Covariant Spectator Quark Model
Energy Technology Data Exchange (ETDEWEB)
G. Ramalho, Franz Gross and M. T. Peña
2010-12-01
We apply the covariant spectator quark–diquark model, already probed in the description of the nucleon elastic form factors, to the calculation of the deep inelastic scattering (DIS) spin-independent and spin-dependent structure functions of the nucleon. The nucleon wave function is given by a combination of quark–diquark orbital states, corresponding to S, D and P-waves. A simple form for the quark distribution function associated to the P and D waves is tested.
Successes and failures of the constituent quark model
Energy Technology Data Exchange (ETDEWEB)
Lipkin, H.J.
1982-01-01
Our approach considers the model as a possible bridge between QCD and the experimental data and examines its predictions to see where these succeed and where they fail. We also attempt to improve the model by looking for additional simple assumptions which give better fits to the experimental data. But we avoid complicated models with too many ad hoc assumptions and too many free parameters; these can fit everything but teach us nothing. We define our constituent quark model by analogy with the constituent electron model of the atom and the constituent nucleon model of the nucleus. In the same way that an atom is assumed to consist only of constituent electrons and a central Coulomb field and a nucleus is assumed to consist only of constituent nucleons hadrons are assumed to consist only of their constituent valence quarks with no bag, no glue, no ocean, nor other constituents. Although these constituent models are oversimplified and neglect other constituents we push them as far as we can. Atomic physics has photons and vacuum polarization as well as constituent electrons, but the constituent model is adequate for calculating most features of the spectrum when finer details like the Lamb shift are neglected. 54 references.
A Euclidean bridge to the relativistic constituent quark model
Hobbs, T J; Miller, Gerald A
2016-01-01
${\\bf Background}$ Knowledge of nucleon structure is today ever more of a precision science, with heightened theoretical and experimental activity expected in coming years. At the same time, a persistent gap lingers between theoretical approaches grounded in Euclidean methods (e.g., lattice QCD, Dyson-Schwinger Equations [DSEs]) as opposed to traditional Minkowski field theories (such as light-front constituent quark models). ${\\bf Purpose}$ Seeking to bridge these complementary worldviews, we explore the potential of a Euclidean constituent quark model (ECQM). This formalism enables us to study the gluonic dressing of the quark-level axial-vector vertex, which we undertake as a test of the framework. ${\\bf Method}$ To access its indispensable elements with a minimum of inessential detail, we develop our ECQM using the simplified quark $+$ scalar diquark picture of the nucleon. We construct a hyperspherical formalism involving polynomial expansions of diquark propagators to marry our ECQM with the results of ...
Constituent quark masses from modified perturbative QCD
Energy Technology Data Exchange (ETDEWEB)
Cabo Montes de Oca, A. [Instituto de Cibernetica, Matematica y Fisica, La Habana (Cuba); International Institute for Theoretical and Applied Physics (IITAP), UNESCO and Iowa State University, Ames, IA (United States); Rigol Madrazo, M. [Centro de Estudios Aplicados al Desarrollo Nuclear, La Habana (Cuba)
2002-03-01
A recently proposed modified perturbative expansion for QCD incorporating gluon condensation is employed to evaluate the quark and gluon self-energy corrections in first approximation. The results predict mass values of 1/3 of the nucleon mass for the light quarks u, d, and s and a monotonously growing variation with the current mass. The only phenomenological input is that left angle G{sup 2} right angle is evaluated up to order g{sup 2} as a function of the unique parameter C defining the modified propagator, and then C is fixed to give a current estimate of left angle g{sup 2}G{sup 2} right angle. The light quarks u and d as a result are found to be confined and the s, c, b and t ones show damped propagation modes, suggesting a model for the large differences in stability between the nucleons and the higher resonances. The above properties of quark modes diverge from the fully confinement result following from the similar gluon propagator previously considered by Munczek and Nemirovski. On the other hand, the condensate effects on the gluon self-energy furnish a tachyonic mass shell as predicted by the Fukuda analysis of gluon condensation in QCD. (orig.)
Meson cloud effects on the pion quark distribution function in the chiral constituent quark model
Watanabe, Akira; Suzuki, Katsuhiko
2016-01-01
We investigate the valence quark distribution function of the pion $v^{\\pi}(x,Q^2)$ in the framework of the chiral constituent quark model and evaluate the meson cloud effects on $v^{\\pi}(x,Q^2)$. We explicitly demonstrate how the meson cloud effects affect $v^{\\pi}(x,Q^2)$ in detail. We find that the meson cloud correction causes an overall 32\\% reduction of the valence quark distribution and an enhancement at the small Bjorken $x$ regime. Besides, we also find that the dressing effect of the meson cloud will make the valence quark distribution to be softer in the large $x$ region.
Constituent quark models and pentaquark baryons
Maltman, K
2004-01-01
We discuss certain general features of the pentaquark picture for the theta, its 10bar_F partner, Xi_{3/2}, and possible heavy quark analogues. Models employing spin-dependent interactions based on either effective Goldstone boson exchange or effective color magnetic exchange are also used to shed light on possible corrections to the Jaffe-Wilczek and Karliner-Lipkin scenarios. Some model-dependent features of the pentaquark picture (splitting patterns and relative decay couplings) are also discussed in the context of these models.
Constituent quark model description of charmonium phenomenology
Segovia, J; Fernandez, F; Hernandez, E
2013-01-01
We review how quark models are able to describe the phenomenology of the charm meson sector. The spectroscopy and decays of charmonium and open charm mesons are described in a particular quark model and compared with the data and the results of other existing models in the literature. A quite reasonable global description of the heavy meson spectra is reached. A new assignment of the $\\psi(4415)$ resonance as a 3D state leaving aside the 4S state to the X(4360) is tested through the analysis of the resonance structure in $e^{+}e^{-}$ exclusive reactions around the $\\psi(4415)$ energy region. We make tentative assignments of some of the $XYZ$ mesons. To elucidate the structure of the $1^{+}$ $c\\bar{s}$ states, i.e. $D_{s1}(2460)$ and $D_{s1}(2536)$, we study the strong decay properties of the $D_{s1}(2536)$ meson. We also perform a calculation of the branching fractions for the semileptonic decays of $B$ and $B_{s}$ mesons into final states containing orbitally excited charmed and charmed-strange mesons, which...
Euclidean bridge to the relativistic constituent quark model
Hobbs, T. J.; Alberg, Mary; Miller, Gerald A.
2017-03-01
Background: Knowledge of nucleon structure is today ever more of a precision science, with heightened theoretical and experimental activity expected in coming years. At the same time, a persistent gap lingers between theoretical approaches grounded in Euclidean methods (e.g., lattice QCD, Dyson-Schwinger equations [DSEs]) as opposed to traditional Minkowski field theories (such as light-front constituent quark models). Purpose: Seeking to bridge these complementary world views, we explore the potential of a Euclidean constituent quark model (ECQM). This formalism enables us to study the gluonic dressing of the quark-level axial-vector vertex, which we undertake as a test of the framework. Method: To access its indispensable elements with a minimum of inessential detail, we develop our ECQM using the simplified quark + scalar diquark picture of the nucleon. We construct a hyperspherical formalism involving polynomial expansions of diquark propagators to marry our ECQM with the results of Bethe-Salpeter equation (BSE) analyses, and constrain model parameters by fitting electromagnetic form factor data. Results: From this formalism, we define and compute a new quantity—the Euclidean density function (EDF)—an object that characterizes the nucleon's various charge distributions as functions of the quark's Euclidean momentum. Applying this technology and incorporating information from BSE analyses, we find the quenched dressing effect on the proton's axial-singlet charge to be small in magnitude and consistent with zero, while use of recent determinations of unquenched BSEs results in a large suppression. Conclusions: The quark + scalar diquark ECQM is a step toward a realistic quark model in Euclidean space, and needs additional refinements. The substantial effect we obtain for the impact on the axial-singlet charge of the unquenched dressed vertex compared to the quenched demands further investigation.
Exploration of hyperfine interaction between constituent quarks via eta productions
He, Jun; Xu, H S
2011-01-01
In this work, the different exchange freedom, one gluon, one pion or Goldstone boson, in constituent quark model is investigated, which is responsible to the hyperfine interaction between constituent quarks, via the combined analysis of the eta production processes, $\\pi^{-}p\\rightarrow\\eta n$ and $\\gamma p\\rightarrow\\eta p$. With the Goldstone-boson exchange, as well as the one-gluon or one-pion exchange, both the spectrum and observables, such as, the differential cross section and polarized beam asymmetry, are fitted to the suggested values of Particle Data Group and the experimental data. The first two types of exchange freedoms give acceptable description of the spectrum and observables while the one pion exchange can not describe the observables and spectrum simultaneously, so can be excluded. The experimental data for the two processes considered here strongly support the mixing angles for two lowest S11 sates and D13 states as about -30 and 6 degree respectively.
Dibaryons with two strange quarks and one heavy flavor in a constituent quark model
Park, Aaron; Park, Woosung; Lee, Su Houng
2016-09-01
We investigate the symmetry property and the stability of dibaryons containing two strange quarks and one heavy flavor with isospin I =1/2 . We construct the wave function of the dibaryon in two ways. First, we directly construct the color and spin state of the dibaryon starting from the four possible S U (3 ) flavor states. Second, we consider the states composed of five light quarks and then construct the wave function of the dibaryon by adding one heavy quark. The stability of the dibaryon against the strong decay into two baryons is discussed by using the variational method in a constituent quark model with a confining and hyperfine potential. We find that, for all configurations with spin S =0 , 1, 2, the ground states of the dibaryons are the sum of two baryons, and there is no compact bound state that is stable against the strong decay.
Dibaryons with two strange quarks and one heavy flavor in a constituent quark model
Park, Aaron; Lee, Su Houng
2016-01-01
We investigate the symmetry property and the stability of dibaryons containing two strange quarks and one heavy flavor with $I=\\frac{1}{2}$. We construct the wave function of the dibaryon in two ways. First, we directly construct the color and spin state of the dibaryon starting from the four possible SU(3) flavor state. Second, we consider the states composed of five light quarks, and then construct the wave function of the dibaryon by adding one heavy quark. The stability of the dibaryon against the strong decay into two baryons is discussed by using variational method in a constituent quark model with confining and hyperfine potential. We find that for all configurations with S=0,1,2, the ground states of the dibaryons are the sum of two baryons, and there are no compact bound state that is stable against the strong decay.
Constituent quark and baryon spectra from a modified Perturbative QCD
Cabo-Montes de Oca, Alejandro; Cabo Montes de Oca, Alejandro; Madrazo, Marcos Rigol
2000-01-01
A recently proposed perturbative expansion for QCD incorporating gluon condensation is employed to evaluate the quark and gluon self-energy corrections in the simplest approximations. The results predict mass values of the order of 1/3 of the nucleon mass for the light quarks u,d and s and a monotonously growing variation with the current mass values. The mass spectrum of the ground states within the various groups of baryonic resonances and a class of vector meson ones is well predicted by the simple addition of the calculated constituent quark masses. In connection with the self-energy, it follows that the gluonic mass shell becomes tachyonic in the considered approximation. In order to obtain the above mentioned results was evaluated as a function of the condensate paramater up to order g^2 and then this parameter fixed to give the accepted numerical value of . The discussion leads us to conjecture that the procedure, after also introducing quark condensates in the same token as the gluonic ones, could a...
A Euclidean bridge to the relativistic constituent quark model
Hobbs, Timothy; Alberg, Mary; Miller, Gerald
2017-01-01
We explore the potential of a Euclidean constituent quark model (ECQM) to bridge the lingering gap between Euclidean and Minkowski field theories in studies of nucleon structure. Specifically, we develop our ECQM using a simplified quark-scalar diquark picture of the nucleon as a first calculation. Our treatment in Euclidean space necessitates a hyperspherical formalism involving polynomial expansions of diquark propagators in order to marry our ECQM with results from Bethe-Salpeter Equation (BSE) analyses. From this framework, we define and compute a new quantity - a Euclidean density function (EDF) - an object that characterizes the nucleon's various charge distributions as functions of the quark's Euclidean momentum. Applying this technology and incorporating information from BSE analyses, we find the quenched dressing effect on the proton's axial-singlet charge to be small in magnitude and consistent with zero, while use of recent determinations of unquenched BSEs results in a large suppression. The substantial effect we obtain for the impact on the axial-singlet charge of the unquenched dressed vertex compared to the quenched demands further investigation. Work supported by DOE grant DE-FG02-97ER-41014 and NSF Grant No. 1516105.
Parton Distribution in Pseudoscalar Mesons with a Light-Front Constituent Quark Model
de Melo, J P B C; Tsushima, Kazuo
2015-01-01
We compute the distribution amplitudes of the pion and kaon in the light-front constituent quark model with the symmetric quark-bound state vertex function. In the calculation we explicitly include the flavor-SU(3) symmetry breaking effect in terms of the constituent quark masses of the up (down) and strange quarks. To calculate the kaon parton distribution functions~(PDFs), we use both the conditions in the light-cone wave function, i.e., when $\\bar{s}$ quark is on-shell, and when $u$ quark is on-shell, and make a comparison between them. The kaon PDFs calculated in the two different conditions clearly show asymmetric behaviour due to the flavor SU(3)-symmetry breaking implemented by the quark masses.
Covariant quark model of form factors in the heavy mass limit
Yaouanc, A. Le; Oliver, L; Pène, O.; Raynal, J. -C.
1995-01-01
We show that quark models of current matrix-elements based on the Bakamjian-Thomas construction of relativistic states with a fixed number of particles, plus the additivity assumption, are covariant in the heavy-quark limit and satisfy the full set of heavy-quark symmetry relations discovered by Isgur and Wise. We find the lower bound of $\\rho^2$ in such models to be $3/4$ for ground state mesons, independently of any parameter. Another welcome property of these models is that in the infinite...
Generalized SU(3) Nambu-Jona-Lasinio model. Pt. 2; From current to constituent quarks
Energy Technology Data Exchange (ETDEWEB)
Vogl, U.; Lutz, M.; Klimt, S.; Weise, W. (Regensburg Univ. (Germany, F.R.). Inst. fuer Physik 1 - Theoretische Physik)
1990-10-08
We investigate the properties of constituent quarks, i.e. quarks dressed by their strong interactions, in a generalized Nambu-Jona-Lasinio model with N{sub f}=3 flavours. In the Hartree-Fock approximation, the step from structureless current quarks to massive constituent quarks is made through dynamical mass generation which implies spontaneous chiral symmetry breaking. We study, in particular, the quark scalar, vector and axial vector currents within this framework. We demonstrate that, a low energy and momentum transfers, single valence quarks are strongly screened by quark-antiquark polarization effects. For the electromagnetic currents, we recover relationships familiar from the vector meson dominance model. For the axial current, screening by J{sup {pi}}=1{sup +} quark-antiquark modes leads to an effective quark axial vector constant g{sub A}<1 which satisfies the Goldberger-Treiman relation at the quark level. The spin content of the proton is also discussed in this framework. We calculate quark magnetic moments and electromagnetic form factors and discuss their related sizes. (orig.).
Constituent quarks and the gluonic contribution to the spin of the nucleon
Energy Technology Data Exchange (ETDEWEB)
Eldahoumi, Gamal
2009-01-15
The internal structure of the nucleon is more complicated than expected in a simple quark model. In particular, the portion of the nucleon spin carried by the spins of the quarks is not, as expected, of the order of one, but according to the experimental data much smaller. In this thesis we study the spin structure of the proton in quantum chromodynamics. The constituent quark model, based on SU(6), predicts that the spin of the proton should be carried by the quarks, in disagreement with the experiments. It appears strange, that the theoretical model works so well for the magnetic moments of the nucleons, but not for the spin, although the spin and the magnetic moments are closely related to each other. We shall resolve this problem by assuming that the constituent quarks have an internal structure on their own. Thus a constituent quark has a dynamical structure, and we can introduce notions like the quark or gluon distributions inside a constituent quark. In the light of new experimental data from HERMES, COMPASS, JLab, and RHIC-spin, the current status of our knowledge of the spin structure is discussed in the two theoretical frameworks: the naive parton model, and the QCD evolved parton model. QCD a is successful theory, both in perturbative and non-perturbative regions, but the spin of the nucleon still needs to be explained within QCD. (orig.)
Gell-Mann, M.
In these lectures I want to speak about at least two interpretations of the concept of quarks for hadrons and the possible relations between them. First I want to talk about quarks as "constituent quarks". These were used especially by G. Zweig (1964) who referred to them as aces. One has a sort of a simple model by which one gets elementary results about the low-lying bound and resonant states of mesons and baryons, and certain crude symmetry properties of these states, by saying that the hadrons act as if they were made up of subunits, the constituent quarks q. These quarks are arranged in an isotopic spin doublet u, d and an isotopic spin singlet s, which has the same charge as d and acts as if it had a slightly higher mass…
The effect of instanton-induced interaction on -wave meson spectra in constituent quark model
Indian Academy of Sciences (India)
Bhavyashri; S Sarangi; Godfrey Saldanha; K B Vijaya Kumar
2008-01-01
The mass spectrum of the -wave mesons is considered in a non-relativistic constituent quark model. The full Hamiltonian used in the investigation includes the kinetic energy, the confinement potential, the one-gluon-exchange potential (OGEP) and the instanton-induced quark-antiquark interaction (III). A good description of the mass spectrum is obtained. The respective role of III and OGEP in the P-wave meson spectrum is discussed.
Ramalho, G
2012-01-01
We study the $\\gamma^\\ast \\Lambda \\to \\Sigma^0$ transition form factors by applying the covariant spectator quark model. Using the parametrization for the baryon core wave functions as well as for the pion cloud dressing obtained in a previous work, we calculate the dependence on the momentum transfer squared, $Q^2$, of the electromagnetic transition form factors. The magnetic form factor is dominated by the valence quark contributions. The final result for the transition magnetic moment, a combination of the quark core and pion cloud effects, turns out to give a value very close to the data. The pion cloud, although small, makes the result towards the data. It is also predicted that small but nonzero values for the electric form factor in the finite $Q^2$ region, as a consequence of the pion cloud dressing.
B --> D$**$ semileptonic decay in covariant quark models à la Bakamjian-Thomas
Morénas, V; Oliver, L; Pène, O; Raynal, J C
1996-01-01
Once chosen the dynamics in one frame, for example the rest frame, the Bakamjian and Thomas method allows to define relativistic quark models in any frame. These models have been shown to provide, in the heavy quark limit, fully covariant current form factors as matrix elements of the quark current operator. They also verify the Isgur-Wise scaling and give a slope parameter \\rho^2>3/4 for all the possible choices of the dynamics. In this paper we study the L=1 excited states and derive the general formula, valid for any dynamics, for the scaling invariant form factors \\tau_{1/2}^{(n)}(w) and \\tau_{3/2}^{(n)}(w). We also check the Bjorken-Isgur-Wise sum rule already demonstrated elsewhere in this class of models.
Quark model with chiral-symmetry breaking and confinement in the Covariant Spectator Theory
Energy Technology Data Exchange (ETDEWEB)
Biernat, Elmer P. [CFTP, Instituto Superior TÃ©cnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; Pena, Maria Teresa [CFTP, Instituto Superior TÃ©cnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; Departamento de FÃsica, Instituto Superior TÃ©cnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; Ribiero, Jose' Emilio F. [CeFEMA, Instituto Superior TÃ©cnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; Stadler, Alfred [Departamento de FÃsica, Universidade de Ãvora, 7000-671 Ãvora, Portugal; Gross, Franz L. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
2016-03-01
We propose a model for the quark-antiquark interaction in Minkowski space using the Covariant Spectator Theory. We show that with an equal-weighted scalar-pseudoscalar structure for the confining part of our interaction kernel the axial-vector Ward-Takahashi identity is preserved and our model complies with the Adler-zero constraint for pi-pi-scattering imposed by chiral symmetry.
Strangeness -2 and -3 Baryons in a Constituent Quark Model
Energy Technology Data Exchange (ETDEWEB)
Muslema Pervin; Winston Roberts
2007-09-19
We apply a quark model developed in earlier work to the spectrum of baryons with strangeness -2 and -3. The model describes a number of well-established baryons successfully, and application to cascade baryons allows the quantum numbers of some known states to be deduced.
Extended Goldstone-boson-exchange constituent quark model
Wagenbrunn, R F; Plessas, W; Varga, K
2000-01-01
We discuss an updated version of the Goldstone-boson-exchange chiral quark model extended to include in addition to pseudoscalar meson exchanges also vector and scalar meson exchanges. The latter ingredients are viewed as effective parametrizations of multiple Goldstone-boson exchanges in baryons. The extended model allows for an accurate description of all light and strange baryon spectra and at the same time produces the right properties for deducing baryon-baryon interactions.
Nucleon structure functions and longitudinal spin asymmetries in the chiral quark constituent model
Dahiya, Harleen
2016-01-01
We have analysed the phenomenological dependence of the spin independent ($F_1^{p,n}$ and $F_2^{p,n}$) and the spin dependent ($g_1^{p,n}$) structure functions of the nucleon on the the Bjorken scaling variable $x$ using the unpolarized distribution functions of the quarks $q(x)$ and the polarized distribution functions of the quarks $\\Delta q(x)$ respectively. The chiral constituent quark model ($\\chi$CQM), which is known to provide a satisfactory explanation of the proton spin crisis and related issues in the nonperturbative regime, has been used to compute explicitly the valence and sea quark flavor distribution functions of $p$ and $n$. In light of the improved precision of the world data, the $p$ and $n$ longitudinal spin asymmetries ($A_1^p(x)$ and $A_1^n(x)$) have been calculated. The implication of the presence of the sea quarks has been discussed for ratio of polarized to unpolarized quark distribution functions for up and down quarks in the $p$ and $n$ $\\frac{\\Delta u^p(x)}{u^p(x)}$, $\\frac{\\Delta d...
The baryon spectrum and the hypercentral Constituent Quark Model
Giannini, M M
2015-01-01
The description of the baryon spectrum is performed using the hypercentral Consituent Quark Model (hCQM), mainly in comparison with the harmonic oscillator (h.o.). Recentlly many new states, at various levels of confidence have been observed, leading to a softening of the missing resonance problem in the case of positive parity states. However, the number of negative states is higher that predicted by the commonly used h.o. scheme and therefore one is forced to take into account also the higher energy shells, which contain an overall number of states much greater than the observed one. It is shown that, thanks to the peculiar level scheme of the hCQM, the recently observed negative parity states can be considered as belonging to the lower shells, keeping the missing resonance problem within more acceptable limits.
The shape of the $\\Delta$ baryon in a covariant spectator quark model
Ramalho, G; Stadler, A
2012-01-01
Using a covariant spectator quark model that describes the recent lattice QCD data for the $\\Delta$ electromagnetic form factors and all available experimental data on $\\gamma N \\to \\Delta$ transitions, we analyze the charge and magnetic dipole distributions of the $\\Delta$ baryon and discuss its shape. We conclude that the quadrupole moment of the $\\Delta$ is a good indicator of the deformation and that the $\\Delta^+$ charge distribution has an oblate shape. We also calculate transverse moments and find that they do not lead to unambiguous conclusions about the underlying shape.
Strong decays of excited 1D charmed(-strange) mesons in the covariant oscillator quark model
Maeda, Tomohito; Yoshida, Kento; Yamada, Kenji; Ishida, Shin; Oda, Masuho
2016-05-01
Recently observed charmed mesons, D1* (2760), D3* (2760) and charmed-strange mesons, Ds1 * (2860), Ds3 * (2860), by BaBar and LHCb collaborations are considered to be plausible candidates for c q ¯ 13 DJ (q = u, d, s) states. We calculate the strong decays with one pion (kaon) emission of these states including well-established 1S and 1P charmed(-strange) mesons within the framework of the covariant oscillator quark model. The results obtained are compared with the experimental data and the typical nonrelativistic quark-model calculations. Concerning the results for 1S and 1P states, we find that, thanks to the relativistic effects of decay form factors, our model parameters take reasonable values, though our relativistic approach and the nonrelativistic quark model give similar decay widths in agreement with experiment. While the results obtained for 13 DJ=1,3 states are roughly consistent with the present data, they should be checked by the future precise measurement.
Calculation of the Isgur-Wise function from a light-front constituent quark model
Simula, S
1996-01-01
The space-like elastic form factor of heavy-light pseudoscalar mesons is investigated within a light-front constituent quark model in order to evaluate the Isgur-Wise form factor. The relativistic composition of the constituent quark spins is properly taken into account using the Melosh rotations, and various heavy-meson wave function are considered, including the eigenfunctions of an effective light-front mass operator reproducing meson mass spectra. It is shown that in a wide range of values of the recoil the Isgur-Wise form factor exhibits a moderate dependence upon the choice of the heavy-meson wave function and is mainly governed by the effects of the confinement scale.
The Nucleon-Nucleon Interaction in a Chiral Constituent Quark Model
Stancu, F; Glozman, L Ya; Stancu, Fl.
1997-01-01
We study the short-range nucleon-nucleon interaction in a chiral constituent quark model by diagonalizing a Hamiltonian comprising a linear confinement and a Goldstone boson exchange interaction between quarks. The six-quark harmonic oscillator basis contains up to two excitation quanta. We show that the highly dominant configuration is $\\mid s^4p^2[42]_O [51]_{FS}>$ due to its specific flavour-spin symmetry. Using the Born-Oppenheimer approximation we find a strong effective repulsion at zero separation between nucleons in both $^3S_1$ and $^1S_0$ channels. The symmetry structure of the highly dominant configuration implies the existence of a node in the S-wave relative motion wave function at short distances. The amplitude of the oscillation of the wave function at short range will be however strongly suppressed. We discuss the mechanism leading to the effective short-range repulsion within the chiral constituent quark model as compared to that related with the one-gluon exchange interaction.
Constituent Quarks and Gluons, Polyakov loop and the Hadron Resonance Gas Model
Megias, E; Salcedo, L L
2013-01-01
Based on first principle QCD arguments, it has been argued in arXiv:1204.2424[hep-ph] that the vacuum expectation value of the Polyakov loop can be represented in the hadron resonance gas model. We study this within the Polyakov-constituent quark model by implementing the quantum and local nature of the Polyakov loop hep-ph/0412308, hep-ph/0607338. The existence of exotic states in the spectrum is discussed.
Constituent Quarks and Gluons, Polyakov loop and the Hadron Resonance Gas Model *,**
Directory of Open Access Journals (Sweden)
Megías E.
2014-03-01
Full Text Available Based on first principle QCD arguments, it has been argued in [1] that the vacuum expectation value of the Polyakov loop can be represented in the hadron resonance gas model. We study this within the Polyakov-constituent quark model by implementing the quantum and local nature of the Polyakov loop [2, 3]. The existence of exotic states in the spectrum is discussed.
On Possible S-Wave Bound States for an N-(N) System Within a Constituent Quark Model
Institute of Scientific and Technical Information of China (English)
CHANG Chao-Hsi; PANG Hou-Rong
2005-01-01
We try to apply a constituent quark model (a variety chiral constituent quark model) and the resonating group approach for the multi-quark problems to compute the effective potential between the NN- in S-wave (the quarks in the nucleons N and N-, and the two nucleons relatively as well, are in S wave) so as to see the possibility if there may be a tight bound state of six quarks as indicated by a strong enhancement at threshold of pp- in J/ψ and B decays. The effective potential which we obtain in terms of the model and approach shows if the experimental enhancement is really caused by a tight S-wave bound state of six quarks, then the quantum number of the bound state is very likely to be I = 1, JPC= 0-+.
Sigma terms of octet baryons in the extended chiral constituent quark model
An, C S
2014-01-01
{\\bf Background:} Quantitative insight into the respective roles played by the valence flavors and the sea quark-antiquark pairs in the baryons is crucial in deepening our comprehension of nonperturbative QCD. {\\bf Purpose:} Study the meson-baryon $\\sigma$-terms for the ground-state octet baryons $B \\equiv N,~\\Lambda,~\\Sigma,~\\Xi$. {\\bf Methods:} Within an extended chiral constituent quark model, we investigate contributions from all possible five-quark components to the $\\sigma$-terms. The probabilities of the quark-antiquark components in the baryons wave functions are calculated by taking the baryons to be admixtures of three- and five-quark components, with the relevant transitions handled {\\it via} the $^{3}P_{0}$ mechanism. {\\bf Results:} Predictions are obtained by using input parameters taken from the literature. Numerical results for the meson-nucleon and the dimensionless ${\\sigma}$-terms, $\\bar {\\sigma}_{Bl}$ and $\\bar {\\sigma}_{Bs}$, are reported. {\\bf Conclusions:} Our results turn out to be, in ...
Heavy-to-Light Form Factors in the Final Hadron Large Energy Limit Covariant Quark Model Approach
Charles, J; Oliver, L; Pène, O; Raynal, J C
1999-01-01
We prove the full covariance of the heavy-to-light weak current matrix elements based on the Bakamjian-Thomas construction of relativistic quark models, in the heavy mass limit for the parent hadron and the large energy limit for the daughter one. Moreover, this quark model representation of the heavy-to-light form factors fulfills the general relations that were recently argued to hold in the corresponding limit of QCD, namely that there are only three independent form factors describing the B -> pi (rho) matrix elements, as well as the factorized scaling law sqrt(M)z(E) of the form factors with respect to the heavy mass M and large energy E. These results constitute another good property of the quark models à la Bakamjian-Thomas, which were previously shown to exhibit covariance and Isgur-Wise scaling in the heavy-to-heavy case.
Charge radii of octet and decuplet baryons in chiral constituent quark model
Indian Academy of Sciences (India)
Neetika Sharma; Harleen Dahiya
2013-09-01
The charge radii of the spin-$\\dfrac{1}{2}^{+}$ octet and spin-$\\dfrac{3}{2}^{+}$ decuplet baryons have been calculated in the framework of chiral constituent quark model ( CQM) using a general parametrization method (GPM). Our results are not only comparable with the latest experimental studies but also agree with other phenomenological models. The effects of (3) symmetry breaking pertaining to the strangeness contribution and GPM parameters pertaining to the one-, two- and three-quark contributions have also been investigated in detail and are found to be the key parameters in understanding the non-zero values for the neutral octet $(n, \\sum^{0}, \\Xi, )$ and decuplet $(^{0}, \\sum^{*0}, \\Xi^{*0})$ baryons.
Chiral symmetry, constituent quarks and quasi-elastic electron-nucleus scattering
Henley, E. M.; Krein, G.
1989-11-01
The effects of chiral symmetry breaking are examined for quasi-elastic electron scattering on nuclei. Nucleons are assumed to be composed of constituent quarks with masses that depend on density. This density dependence is determined on the basis of the Nambu-Jona-Lasinio model. It is found that the effects of chiral symmetry breaking are in the right direction and the right order of magnitude to explain the discrepancies between theory and experiment. On leave from Departamento de Fisica, Universidade Federal de Santa Maria, 97100 Santa Maria, R.S., Brazil.
Nucleon shape and electromagnetic form factors in the chiral constituent quark model
Dahiya, Harleen
2010-01-01
The electromagnetic form factors are the most fundamental quantities to describe the internal structure of the nucleon and the shape of a spatially extended particle is determined by its intrinsic quadrupole moment which can be related to the charge radii. We have calculated the electromagnetic form factors, nucleon charge radii and the intrinsic quadrupole moment of the nucleon in the framework of chiral constituent quark model. The results obtained are comparable to the latest experimental studies and also show improvement over some theoretical interpretations.
Differential elliptic flow of identified hadrons and constituent quark number scaling at FAIR
Bhaduri, Partha Pratim; Chattopadhyay, Subhasis
2010-01-01
Differential elliptic flow $v_2(p_{T})$ for identified hadrons has been investigated in the FAIR energy regime, employing a hadronic-string transport model (UrQMD) as well as a partonic transport model (AMPT). It has been observed that both the models show a mass ordering of $v_2$ at low $p_{T}$ and a switch over resulting a baryon-meson crossing at intermediate $p_{T}$. AMPT generates higher $v_2$ values compared to UrQMD. In addition, constituent quark number scaling behavior of elliptic fl...
NN S-Wave Elastic Cross Section and Possible Bound States in a Constituent Quark Model
Institute of Scientific and Technical Information of China (English)
PANG Hou-Rong; PING Jia-Lun; WANG Fan
2008-01-01
In the framework of a chiral constituent quark model, considering the contributions of π annihilation and one-gluon annihilation, the proton-antiproton s-wave elastic scattering cross section experimental data can be reproduced by adjusting properly one-gluon annihilation coupling constant. After fixing the model parameters, we perform a dynamical calculation for all possible s-wave nucleon-antinucleon states. The results show that there is no s-wave bound state as indicated by a strong enhancement at threshold of pp in J/ψ and B decay.
Solitons as baryons and qualitons as constituent quarks in two-dimensional QCD
Blas, H
2008-01-01
We study the soliton type solutions arising in two-dimensional quantum chromodynamics (QCD$_{2}$). The so-called generalized sine-Gordon model (GSG) arises as the low-energy effective action of bosonized QCD$_{2}$ for unequal quark mass parameters, and it has been shown that the relevant solitons describe the normal and exotic baryonic spectrum of QCD$_{2}$ [JHEP(03)(2007)(055)]. In the first part of this chapter we classify the soliton and kink type solutions of the sl(3) GSG model. Related to the GSG model we consider the sl(3) affine Toda model coupled to matter fields (Dirac spinors) (ATM). It has been shown the confinement of the spinors inside the solitons and kinks of the GSG model providing an extended hadron model for "quark" confinement [JHEP(01)(2007)(027)]. In the second part of this chapter we discuss the appearance of the constituent quarks in the context of bosonized QCD$_{2}$ and the relevance of the $sl(2)$ ATM model in order to describe the confinement of the color degrees of freedom. We hav...
Constituent Quarks and Gluons, Polyakov loop and the Hadron Resonance Gas Model ***
Megías, E.; Ruiz Arriola, E.; Salcedo, L. L.
2014-03-01
Based on first principle QCD arguments, it has been argued in [1] that the vacuum expectation value of the Polyakov loop can be represented in the hadron resonance gas model. We study this within the Polyakov-constituent quark model by implementing the quantum and local nature of the Polyakov loop [2, 3]. The existence of exotic states in the spectrum is discussed. Presented by E. Megías at the International Nuclear Physics Conference INPC 2013, 2-7 June 2013, Firenze, Italy.Supported by Plan Nacional de Altas Energías (FPA2011-25948), DGI (FIS2011-24149), Junta de Andalucía grant FQM-225, Spanish Consolider-Ingenio 2010 Programme CPAN (CSD2007-00042), Spanish MINECO's Centro de Excelencia Severo Ochoa Program grant SEV-2012-0234, and the Juan de la Cierva Program.
Relativistic effects on the neutron charge form factor in the constituent quark model
Cardarelli, F
1999-01-01
The neutron charge form factor GEn(Q**2) is investigated within a constituent quark model formulated on the light-front. It is shown that, if the quark initial motion is neglected in the Melosh rotations, the Dirac neutron form factor F1n(Q**2) receives a relativistic correction which cancels exactly against the Foldy term in GEn(Q**2), as it has been recently argued by Isgur. Moreover, at the same level of approximation the ratio of the proton to neutron magnetic form factors GMp(Q**2)/GMn(Q**2) is still given by the naive SU(6)-symmetry expectation, -3/2. However, it is also shown that the full Melosh rotations break SU(6) symmetry, giving rise to GEn(Q**2) neq 0 and GMp(Q**2)/GMn(Q**2) neq -3/2 even when a SU(6)-symmetric canonical wave function is assumed. It turns out that relativistic effects alone cannot explain simultaneously the experimental data on GEn(Q**2) and GMp(Q**2)/GMn(Q**2).
Energy Technology Data Exchange (ETDEWEB)
Albaladejo, M.; Fernandez-Soler, P.; Nieves, J.; Ortega, P.G. [Centro Mixto CSIC-Universidad de Valencia, Instituto de Fisica Corpuscular (IFIC), Institutos de Investigacion de Paterna, Aptd. 22085, Valencia (Spain)
2017-03-15
The discovery of the D{sup *}{sub s0}(2317) and D{sub s1}(2460) resonances in the charmed-strange meson spectra revealed that formerly successful constituent quark models lose predictability in the vicinity of two-meson thresholds. The emergence of non-negligible effects due to meson loops requires an explicit evaluation of the interplay between Q anti q and (Q anti q)(q anti q) Fock components. In contrast to the c anti s sector, there is no experimental evidence of J{sup P} = 0{sup +}, 1{sup +} bottom-strange states yet. Motivated by recent lattice studies, in this work the heavy-quark partners of the D{sub s0}{sup *}(2317) and D{sub s1}(2460) states are analyzed within a heavy meson chiral unitary scheme. As a novelty, the coupling between the constituent quark-model P-wave anti B{sub s} scalar and axial mesons and the anti B{sup (*)}K channels is incorporated employing an effective interaction, consistent with heavy-quark spin symmetry, constrained by the lattice energy levels. (orig.)
On the constituent counting rule for hard exclusive processes involving multi-quark states
Guo, Feng-Kun; Meißner, Ulf-G.; Wang, Wei
2017-05-01
At high energy, the cross section at finite scattering angle of a hard exclusive process falls off as a power of the Manderstam variable s. If all involved quark-gluon compositions undergo hard momentum transfers, the fall-off scaling is determined by the underlying valence structures of the initial and final hadrons, known as the constituent counting rule. In spite of the complication due to helicity conservation, it has been argued that when applied to exclusive process with exotic multiquark states, the counting rule is a powerful way to determine the valence degrees of freedom inside hadron exotics. In this work, we demonstrate that for hadrons with hidden flavors, the naive application of the constituent counting rule to exclusive process with hadron exotic multiquark states is problematic, since it is not mandatory for all components to participate in hard scattering at the scale . We illustrate the problems in the viewpoint based on effective field theory. We clarify the misleading results that may be obtained from the constituent counting rule in exclusive processes with exotic candidates such as , , X(3872), etc. Supported in part by DFG and NSFC through funds provided to the Sino-German CRC 110 “Symmetries and the Emergence of Structure in QCD” (NSFC Grant No. 11261130311), Thousand Talents Plan for Young Professionals, Chinese Academy of Sciences (CAS) President’s International Fellowship Initiative (PIFI) (2015VMA076), National Natural Science Foundation of China (11575110, 11655002), Natural Science Foundation of Shanghai (15DZ2272100, 15ZR1423100), Open Project Program of State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, China (Y5KF111CJ1), and by Key Laboratory for Particle Physics, Astrophysics and Cosmology, Ministry of Education.
How I got to work with Feynman on the covariant quark model
Ravndal, Finn
2014-01-01
In the period 1968 - 1974 I was a graduate student and then a postdoc at Caltech and was involved with the developments of the quark and parton models. Most of this time I worked in close contact with Richard Feynman and thus was present from the parton model was proposed until QCD was formulated. A personal account is presented how the collaboration took place and how the various stages of this development looked like from the inside until QCD was established as a theory for strong interactions with the partons being quarks and gluons.
A pure S-wave covariant model for the nucleon
Gross, F; Peña, M T; Gross, Franz
2006-01-01
Using the manifestly covariant spectator theory, and modeling the nucleon as a system of three constituent quarks with their own electromagnetic structure, we show that all four nucleon electromagnetic form factors can be very well described by a manifestly covariant nucleon wave function with zero orbital angular momentum.
A Gauge and Lorentz covariant Approximation for the Quark Propagator in an arbitrary Gluon Field
Gromes, D
2001-01-01
We decompose the quark propagator in the presence of an arbitrary gluon field with respect to a set of Dirac matrices. The four-dimensional integrals which arise in first order perturbation theory are rewritten as line-integrals along certain field lines, together with a weighted integration over the various field lines. It is then easy to transform the propagator into a form involving path ordered exponentials. The resulting expression is non-perturbative and has the correct behavior under Lorentz transformations, gauge transformations and charge conjugation. Furthermore it coincides with the exact propagator in first order of the coupling g. No expansion with respect to the inverse quark mass is involved, the expression can even be used for vanishing mass. For large mass the field lines concentrate near the straight line connection and simple results can be obtained immediately.
A Gauge and Lorentz covariant approximation for the quark propagator in an arbitrary gluon field
Gromes, D.
2001-05-01
We decompose the quark propagator in the presence of an arbitrary gluon field with respect to a set of Dirac matrices. The four-dimensional integrals which arise in first order perturbation theory are rewritten as line-integrals along certain field lines, together with a weighted integration over the various field lines. It is then easy to transform the propagator into a form involving path ordered exponentials. The resulting expression is non-perturbative and has the correct behavior under Lorentz transformations, gauge transformations and charge conjugation. Furthermore it coincides with the exact propagator in first order of the coupling g. No expansion with respect to the inverse quark mass is involved, the expression can even be used for vanishing mass. For large mass the field lines concentrate near the straight line connection and simple results can be obtained immediately.
Covariant nucleon wave function with S, D, and P-state components
Gross, Franz; Pena, M T
2012-01-01
Expressions for the nucleon wave functions in the covariant spectator theory (CST) are derived. The nucleon is described as a system with a off-mass-shell constituent quark, free to interact with an external probe, and two spectator constituent quarks on their mass shell. Integrating over the internal momentum of the on-mass-shell quark pair allows us to derive an effective nucleon wave function that can be written only in terms of the quark and diquark (quark-pair) variables. The derived nucleon wave function includes contributions from S, P and D-waves.
Covariant nucleon wave function with S, D, and P-state components
Energy Technology Data Exchange (ETDEWEB)
Franz Gross, G. Ramalho, M. T. Pena
2012-05-01
Expressions for the nucleon wave functions in the covariant spectator theory (CST) are derived. The nucleon is described as a system with a off-mass-shell constituent quark, free to interact with an external probe, and two spectator constituent quarks on their mass shell. Integrating over the internal momentum of the on-mass-shell quark pair allows us to derive an effective nucleon wave function that can be written only in terms of the quark and diquark (quark-pair) variables. The derived nucleon wave function includes contributions from S, P and D-waves.
Quarkonia and heavy-light mesons in a covariant quark model
Directory of Open Access Journals (Sweden)
Leitão Sofia
2016-01-01
Full Text Available Preliminary calculations using the Covariant Spectator Theory (CST employed a scalar linear confining interaction and an additional constant vector potential to compute the mesonic mass spectra. In this work we generalize the confining interaction to include more general structures, in particular a vector and also a pseudoscalar part, as suggested by a recent study [1]. A one-gluon-exchange kernel is also implemented to describe the short-range part of the interaction. We solve the simplest CST approximation to the complete Bethe-Salpeter equation, the one-channel spectator equation, using a numerical technique that eliminates all singularities from the kernel. The parameters of the model are determined through a fit to the experimental pseudoscalar meson spectra, with a good agreement for both quarkonia and heavy-light states.
Jung, Ju-Hyun
2016-01-01
We present a microscopic description of the strong $\\pi NN$, $\\pi N\\Delta$ and $\\pi\\Delta\\Delta$ vertices. Our starting point is a constituent-quark model supplemented by an additional $3q\\pi$ non-valence component. In the spirit of chiral constituent-quark models, quarks are allowed to emit and reabsorb a pion. This multichannel system is treated in a relativistically invariant way within the framework of point-form quantum mechanics. Starting with a common $SU(6)$ spin-flavor-symmetric wave function for $N$ and $\\Delta$, we calculate the strength of the $\\pi NN$, $\\pi N\\Delta$ and $\\pi\\Delta\\Delta$ couplings and the corresponding vertex form factors. Our results are in accordance with phenomenological fits of these quantities that have been obtained within purely hadronic multichannel models for baryon resonances.
Mitchell, J T; Tannenbaum, M J; Stankus, P W
2016-01-01
Several methods of generating three constituent-quarks in a nucleon are evaluated which explicitly maintain the nucleon's center of mass and desired radial distribution and can be used within Monte Carlo Glauber frameworks. The geometric models provided by each method are used to generate distributions over the Number of Constituent Quark Participants ($N_{qp}$) in $p+p$, $d+$Au and Au$+$Au collisions. The results are compared with each other and to a previous result of $N_{qp}$ calculations, without this explicit constraint, used in measurements of $\\sqrt{s_{_{NN}}}$=200 GeV $p+p$, $d+$Au and Au$+$Au collisions at RHIC.
Energy Technology Data Exchange (ETDEWEB)
Barbara Pasquini, Peter Schweitzer
2011-06-01
We present results for leading-twist azimuthal asymmetries in semi-inclusive lepton-nucleon deep-inelastic scattering due to naively time-reversal odd transverse-momentum dependent parton distribution functions from the light-cone constituent quark model. We carefully discuss the range of applicability of the model, especially with regard to positivity constraints and evolution effects. We find good agreement with available experimental data from COMPASS and HERMES, and present predictions to be tested in forthcoming experiments at Jefferson Lab.
Electromagnetic properties of light and heavy baryons in the relativistic quark model
Energy Technology Data Exchange (ETDEWEB)
Nicmorus Marinescu, Diana
2007-06-14
One of the main challenges of nowadays low-energy physics remains the description of the internal structure of hadrons, strongly connected to the electromagnetic properties of matter. In this vein, the success of the relativistic quark model in the analysis of the hadron structure constitutes a solid motivation for the study carried out throughout this work. The relativistic quark model is extended to the investigation of static electromagnetic properties of both heavy and light baryons. The bare contributions to the magnetic moments of the single-, double- and triple-heavy baryons are calculated. Moreover, the relativistic quark model allows the study of the electromagnetic properties of the light baryon octet incorporating meson cloud contributions in a perturbative manner. The long disputed values of the multipole ratios E2/M1 and C2/M1 and the electromagnetic form factors of the N{yields}{delta}{gamma} transition are successfully reproduced. The relativistic quark model can be viewed as a quantum field theory approach based on a phenomenological Lagrangian coupling light and heavy baryons to their constituent quarks. In our approach the baryon is a composite object of three constituent quarks, at least in leading order. The effective interaction Lagrangian is written in terms of baryon and constituent quark fields. The effective action preserves Lorentz covariance and gauge invariance. The main ingredients of the model are already introduced at the level of the interaction Lagrangian: the three-quark baryon currents, the Gaussian distribution of the constituent quarks inside the baryon and the compositeness condition which sets an upper limit for the baryon-quark vertex. The S-matrix elements are expressed by a set of Feynman quark-diagrams. The model contains only few parameters, namely, the cut-off parameter of the Gaussian quark distribution and the free quark propagator, which are unambiguously determined from the best fit to the data. The heavy quark limit
Quark structure of chiral solitons
Diakonov, D
2004-01-01
There is a prejudice that the chiral soliton model of baryons is something orthogonal to the good old constituent quark models. In fact, it is the opposite: the spontaneous chiral symmetry breaking in strong interactions explains the appearance of massive constituent quarks of small size thus justifying the constituent quark models, in the first place. Chiral symmetry ensures that constituent quarks interact very strongly with the pseudoscalar fields. The ``chiral soliton'' is another word for the chiral field binding constituent quarks. We show how the old SU(6) quark wave functions follow from the ``soliton'', however, with computable relativistic corrections and additional quark-antiquark pairs. We also find the 5-quark wave function of the exotic baryon Theta+.
B{sup ¯}{sub s}→K semileptonic decay from an Omnès improved constituent quark model
Energy Technology Data Exchange (ETDEWEB)
Albertus, C. [Departamento de Física Atómica, Nuclear y Molecular e Instituto Carlos I de Física Teórica y Computacional, Universidad de Granada, Avenida de Fuentenueva s/n, E-18071 Granada (Spain); Hernández, E. [Departamento de Física Fundamental e IUFFyM, Universidad de Salamanca, Plaza de la Merced s/n, E-37008 Salamanca (Spain); Hidalgo-Duque, C.; Nieves, J. [Instituto de Física Corpuscular (IFIC), Centro Mixto CSIC-Universidad de Valencia, Institutos de Investigación de Paterna, Apartado 22085, E-46071 Valencia (Spain)
2014-11-10
We study the f{sup +} form factor for the semileptonic B{sup ¯}{sub s}→K{sup +}ℓ{sup −}ν{sup ¯}{sub ℓ} decay in a constituent quark model. The valence quark estimate is supplemented with the contribution from the B{sup ¯⁎} pole that dominates the high q{sup 2} region. We use a multiply-subtracted Omnès dispersion relation to extend the quark model predictions from its region of applicability near q{sub max}{sup 2}=(M{sub B{sub s}}−M{sub K}){sup 2}∼23.75 GeV{sup 2} to all q{sup 2} values accessible in the physical decay. To better constrain the dependence of f{sup +} on q{sup 2}, we fit the subtraction constants to a combined input from previous light cone sum rule by Duplancic and Melic (2008) [11] and the present quark model results. From this analysis, we obtain Γ(B{sup ¯}{sub s}→K{sup +}ℓ{sup −}ν{sup ¯}{sub ℓ})=(5.47{sub −0.46}{sup +0.54})|V{sub ub}|{sup 2}×10{sup −9} MeV, which is about 10% and 20% higher than the predictions based on Lattice QCD and QCD light cone sum rules respectively. The former predictions, for both the form factor f{sup +}(q{sup 2}) and the differential decay width, lie within the 1σ band of our estimated uncertainties for all q{sup 2} values accessible in the physical decay, except for a quite small region very close to q{sub max}{sup 2}. Differences with the light cone sum results for the form factor f{sup +} are larger than 20% in the region above q{sup 2}=15 GeV{sup 2}.
Quark Models and Quark Phenomenology
Lipkin, Harry Jeannot
1997-01-01
Overwhelming experimental evidence for quarks as real physical constituents of hadrons along with the QCD analogs of the Balmer Formula, Bohr Atom and Schroedinger Equation already existed in 1966. A model of colored quarks interacting with a one-gluon-exchange potential explained the systematics of the meson and baryon spectrum and gave a hadron mass formula in surprising agreement with experiment. The simple quark model dismissed as heresy and witchcraft by the establishment predicted quantum numbers of an enormous number of hadronic states as well as relations between masses, reaction cross sections and electromagnetic properties, all unexplained by other approaches. Further developments leading to QCD included confinement in the large $N_c$ limit, duality, dual resonance and string models, high energy scattering systematics, unified treatment of mesons and baryons, no exotics and no free quarks.
A covariant formalism for the N* electroproduction at high momentum transfer
Energy Technology Data Exchange (ETDEWEB)
Gilberto Ramalho,Franz Gross,Maria Haderer De La Pena S,Kazuo Tsushima
2011-05-01
A constituent quark model based on the spectator formalism is applied to the gamma N -> N* transition for the three cases, where N* is the nucleon, the Delta and the Roper resonance. The model is covariant, and therefore can be used for the predictions at higher four-momentum transfer squared, Q2. The baryons are described as an off-mass-shell quark and a spectator on-mass-shell diquark systems. The quark electromagnetic current is described by quark form factors, which have a form inspired by the vector meson dominance. The valence quark contributions of the model are calibrated by lattice QCD simulations and experimental data. Contributions of the meson cloud to the inelastic processes are explicitly included.
A covariant formalism for the N* electroproduction at high momentum transfer
Ramalho, G; Pena, M T; Tsushima, K
2010-01-01
A constituent quark model based on the spectator formalism is applied to the gamma N -> N* transition for the three cases, where N* is the nucleon, the Delta and the Roper resonance. The model is covariant, and therefore can be used for the predictions at higher four-momentum transfer squared, Q2. The baryons are described as an off-mass-shell quark and a spectator on-mass-shell diquark systems. The quark electromagnetic current is described by quark form factors, which have a form inspired by the vector meson dominance. The valence quark contributions of the model are calibrated by lattice QCD simulations and experimental data. Contributions of the meson cloud to the inelastic processes are explicitly included.
Choi, Ho-Meoyng
2014-01-01
We discuss the light-front zero-mode issue in the light-front quark model prediction of the twist-3 distribution amplitude of a pseudoscalar meson from the perspective of the vacuum fluctuation consistent with the chiral symmetry of QCD.
Baryons in the unquenched quark model
Bijker, R; Lopez-Ruiz, M A; Santopinto, E
2016-01-01
In this contribution, we present the unquenched quark model as an extension of the constituent quark model that includes the effects of sea quarks via a $^{3}P_{0}$ quark-antiquark pair-creation mechanism. Particular attention is paid to the spin and flavor content of the proton, magnetic moments and $\\beta$ decays of octet baryons.
A covariant model for the gamma N -> N(1535) transition at high momentum transfer
Ramalho, G
2011-01-01
A relativistic constituent quark model is applied to the gamma N -> N(1535) transition. The N(1535) wave function is determined by extending the covariant spectator quark model, previously developed for the nucleon, to the S11 resonance. The model allows us to calculate the valence quark contributions to the gamma N -> N(1535) transition form factors. Because of the nucleon and N(1535) structure the model is valid only for Q^2> 2.3 GeV^2. The results are compared with the experimental data for the electromagnetic form factors F1* and F2* and the helicity amplitudes A_1/2 and S_1/2, at high Q^2.
A covariant model for the gamma N -> N(1535) transition at high momentum transfer
Energy Technology Data Exchange (ETDEWEB)
G. Ramalho, M.T. Pena
2011-08-01
A relativistic constituent quark model is applied to the gamma N -> N(1535) transition. The N(1535) wave function is determined by extending the covariant spectator quark model, previously developed for the nucleon, to the S11 resonance. The model allows us to calculate the valence quark contributions to the gamma N -> N(1535) transition form factors. Because of the nucleon and N(1535) structure the model is valid only for Q^2> 2.3 GeV^2. The results are compared with the experimental data for the electromagnetic form factors F1* and F2* and the helicity amplitudes A_1/2 and S_1/2, at high Q^2.
A Covariant model for the nucleon and the $\\Delta$
Ramalho, G; Gross, Franz
2008-01-01
The covariant spectator formalism is used to model the nucleon and the $\\Delta$(1232) as a system of three constituent quarks with their own electromagnetic structure. The definition of the ``fixed-axis'' polarization states for the diquark emitted from the initial state vertex and absorbed into the final state vertex is discussed. The helicity sum over those states is evaluated and seen to be covariant. Using this approach, all four electromagnetic form factors of the nucleon, together with the {\\it magnetic} form factor, $G_M^*$, for the $\\gamma N \\to \\Delta$ transition, can be described using manifestly covariant nucleon and $\\Delta$ wave functions with {\\it zero} orbital angular momentum $L$, but a successful description of $G_M^*$ near $Q^2=0$ requires the addition of a pion cloud term not included in the class of valence quark models considered here. We also show that the pure $S$-wave model gives electric, $G_E^*$, and coulomb, $G^*_C$, transition form factors that are identically zero, showing that th...
Static quark-antiquark potential
Energy Technology Data Exchange (ETDEWEB)
Deo, B.B.; Barik, B.K.
1983-01-01
A heavy-quark--antiquark potential is suggested which connects asymptotic freedom and quark confinement in a unified manner by formal methods of field theory using some plausible assumptions. The potential has only one additional adjustable parameter B which is proportional to (M/sub q//m/sub q/), where M/sub q/ and m/sub q/ are the constituent and current quark masses, respectively.
The quark revolution and the ZGS - new quarks physics since the ZGS
Energy Technology Data Exchange (ETDEWEB)
Lipkin, H.J. [Weizmann Institute of Science, Rehovot (Israel)]|[Tel Aviv Univ. (Israel)
1994-12-31
Overwhelming experimental evidence for quarks as real physical constituents of hadrons along with the QCD analogs of the Balmer Formula, Bohr Atom and Schroedinger Equation already existed in 1966 but was dismissed as heresy. ZGS experiments played an important role in the quark revolution. This role is briefly reviewed and subsequent progress in quark physics is described.
Electromagnetic structure of the Delta baryon within the covariant spectator theory
Energy Technology Data Exchange (ETDEWEB)
M. T. Pena, G. Ramalho, Franz Gross
2010-12-01
We calculated all the electromagnetic observables for the nucleon and its lowest-lying Delta(1232) excitation within a constituent quark model for those two baryons based on the covariant spectator theory. Once the reactions gamma N \\to N and gamma N \\to Delta were described, we predicted without further adjusting of parameters the four electromagnetic Delta form factors: the electric charge G_{E0}, the magnetic dpole G_{M1}, the electric quadrupole G_{E2} and the magnetic octupole G_{M3}. The results are compatible with the available experimental data and recent lattice QCD data.
Quark and pion effective couplings from polarization effects
Braghin, Fabio L
2016-01-01
A flavor SU(2) effective model for pions and quarks is derived by considering polarization effects departing from the usual quark-quark effective interaction induced by dressed gluon exchange, i.e. a global color model for QCD. For that, the quark field is decomposed into a component that yields light mesons and the quark-antiquark condensate, being integrated out by means of the auxiliary field method, and another component which yields constituent quarks. Within a longwavelength and weak quark field expansion (or large quark effective mass expansion) of a quark determinant, the leading terms are found up to the second order in a zero order derivative expansion, by neglecting vector mesons that are considerably heavier than the pion. Pions are considered in the structureless limit and, besides the chiral invariant pion self interaction terms that reproduce previously derived expressions, symmetry breaking terms are also presented. The leading chiral quark-quark effective couplings are also found correspondin...
Magnetic moments of heavy baryons in the relativistic three-quark model
Faessler, A; Ivanov, M A; Körner, J G; Lyubovitskij, V E; Nicmorus, D; Pumsa-ard, K; Faessler, Amand; Gutsche, Th.
2006-01-01
The magnetic moments of ground state single, double and triple heavy baryons containing charm or bottom quarks are calculated in a relativistic three-quark model, which, in the heavy quark limit, is consistent with Heavy Quark Effective Theory and Heavy Hadron Chiral Perturbation Theory. The internal quark structure of baryons is modeled by baryonic three-quark currents with a spin-flavor structure patterned according to standard covariant baryonic wave functions and currents used in QCD sum rule calculations.
Quantifying zig-zag motion of quarks
Antonov, D
2010-01-01
Quark condensate is calculated in terms of the effective string tension and the constituent quark mass. For 3 colors and 2 light flavors, the constituent mass is bounded from below by the value of 460 MeV. This value is only accessible when the string tension decreases linearly with the Schwinger proper time. For this reason, the Hausdorff dimension of a light-quark trajectory is equal to 4, indicating that these trajectories are similar to branched polymers, which can describe a weak first-order deconfinement phase transition in SU(3) Yang-Mills theory. Using this indication, we develop a gluon-chain model based on such trajectories.
A Diquark-Quark Model with Its Use in Nucleon Form Factors
Institute of Scientific and Technical Information of China (English)
WANG Hong-Min; ZHANG Ben-Ai
2005-01-01
The nucleon electromagnetic form factors are investigated within a simple diquark-quark model using the light-front formalism. In this model, baryon is described as a bound state of one quark and one clustering diquark.The calculational results are compared with the experimental ones. We also regard the quarks in a baryon as pointlike constituent quarks.
Relativistic Three-Quark Bound States in Separable Two-Quark Approximation
Öttel, M; Alkofer, R
2002-01-01
Baryons as relativistic bound states in 3-quark correlations are described by an effective Bethe-Salpeter equation when irreducible 3-quark interactions are neglected and separable 2-quark correlations are assumed. We present an efficient numerical method to calculate the nucleon mass and its covariant wave function in this quantum field theoretic quark-diquark model with quark-exchange interaction. Expanding the components of the spinorial wave function in terms of Chebyshev polynomials, the four-dimensional integral equations are in a first step reduced to a coupled set of one-dimensional ones. This set of linear and homogeneous equations defines a generalised eigenvalue problem. Representing the eigenvector corresponding to the largest eigenvalue, the Chebyshev moments are then obtained by iteration. The nucleon mass is implicitly determined by the eigenvalue, and its covariant wave function is reconstructed from the moments within the Chebyshev approximation.
Quark and pion effective couplings from polarization effects
Energy Technology Data Exchange (ETDEWEB)
Braghin, Fabio L. [Federal University of Goias, Instituto de Fisica, Goiania, GO (Brazil)
2016-05-15
A flavor SU(2) effective model for pions and quarks is derived by considering polarization effects departing from the usual quark-quark effective interaction induced by dressed gluon exchange, i.e. a global color model for QCD. For that, the quark field is decomposed into a component that yields light mesons and the quark-antiquark condensate, being integrated out by means of the auxiliary field method, and another component which yields constituent quarks, which is basically a background quark field. Within a long-wavelength and weak quark field expansion (or large quark effective mass expansion) of a quark determinant, the leading terms are found up to the second order in a zero-order derivative expansion, by neglecting vector mesons that are considerably heavier than the pion. Pions are considered in the structureless limit and, besides the chiral invariant terms that reproduce previously derived expressions, symmetry breaking terms are also presented. The leading chiral quark-quark effective couplings are also found corresponding to a NJL and a vector-NJL couplings. All the resulting effective coupling constants and parameters are expressed in terms of the current and constituent quark masses and of the coupling g. (orig.)
Linear Chemical Potential Dependence of Two-Quark Condensate
Institute of Scientific and Technical Information of China (English)
ZONG Hong-Shi; SUN Wei-Min
2006-01-01
By differentiating the inverse dressed quark propagator at finite chemical potential μ with respect to μ, the linear response of the dressed quark propagator to the chemical potential can be obtained. From this we extract a modelindependent formula for the linear chemical potential dependence of the in-medium two-quark condensate and show by two independent methods (explicit calculation and Lorentz covariance arguments) that the first-order contribution in μto the in-medium two-quark condensate vanishes identically. Therefore if one wants to study the in-medium two-quark condensate one should expand to at least the second order in the chemical potential μ.
Quark-gluon vertex in arbitrary gauge and dimension
Davydychev, A I; Saks, L
2001-01-01
One-loop off-shell contributions to the quark-gluon vertex are calculated, in an arbitrary covariant gauge and in arbitrary space-time dimension, including quark-mass effects. It is shown how one can get results for all on-shell limits of interest directly from the off-shell expressions. In order to demonstrate that the Ward-Slavnov-Taylor identity for the quark-gluon vertex is satisfied, we have also calculated the corresponding one-loop contribution involving the quark-quark-ghost-ghost vertex.
Quark Number Scaling in Fluid Dynamics and Hadronization via Quarkyonic Matter
Directory of Open Access Journals (Sweden)
Zschocke S.
2011-04-01
Full Text Available NCQ scaling of elliptic flow is studied in a non-equilibrium hadronization and freeze-out model from ideal, deconfined and chirally symmetric Quark Gluon Plasma (QGP, to final non-interacting hadrons. In this transition the quarks gain constituent quark mass while the background Bag-field breaks up. The constituent quarks then recombine into simplified hadron states, while chemical, thermal and flow equilibrium break down. Then the resulting temperatures and flow velocities of baryons and mesons will be different. In a simplified model, we reproduce the constituent quark number scaling.
Nuclear matter from effective quark-quark interaction.
Baldo, M; Fukukawa, K
2014-12-12
We study neutron matter and symmetric nuclear matter with the quark-meson model for the two-nucleon interaction. The Bethe-Bruckner-Goldstone many-body theory is used to describe the correlations up to the three hole-line approximation with no extra parameters. At variance with other nonrelativistic realistic interactions, the three hole-line contribution turns out to be non-negligible and to have a substantial saturation effect. The saturation point of nuclear matter, the compressibility, the symmetry energy, and its slope are within the phenomenological constraints. Since the interaction also reproduces fairly well the properties of the three-nucleon system, these results indicate that the explicit introduction of the quark degrees of freedom within the considered constituent quark model is expected to reduce the role of three-body forces.
Relativistic quark model for the Omega- electromagnetic form factors
Energy Technology Data Exchange (ETDEWEB)
G. Ramalho, K. Tsushima, Franz Gross
2009-08-01
We compute the Omega- electromagnetic form factors and the decuplet baryon magnetic moments using a quark model application of the Covariant Spectator Theory. Our predictions for the Omega- electromagnetic form factors can be tested in the future by lattice QCD simulations at the physical strange quark mass.
A relativistic quark model for the Omega- electromagnetic form factors
Ramalho, G; Gross, Franz
2009-01-01
We compute the Omega- electromagnetic form factors and the decuplet baryon magnetic moments using a quark model application of the Covariant Spectator Theory. Our predictions for the Omega- electromagnetic form factors can be tested in the future by lattice QCD simulations at the physical strange quark mass.
The Spectral Quark Model and Light Cone Phenomenology
Ruiz-Arriola, E; Broniowsk, Wojciech
2003-01-01
Chiral quark models offer a practical and simple tool to describe covariantly both low and high energy phenomenology in combination with QCD evolution. This can be done in full harmony with chiral symmetry and electromagnetic gauge invariance. We review the recently proposed spectral quark model where all these constraints are implemented.
Menke, Sven; The ATLAS collaboration
2017-01-01
The top quark is the heaviest known fundamental particle. As it is the only quark that decays before it hadronises, analyses of events containing top quarks allow to probe the properties of bare quarks and to test perturbative QCD. This talk will focus on recent precision top-quark measurements by the ATLAS Collaboration: Single top-quark and top-quark pair production cross sections including differential distributions will be presented, as well as measurements of top-quark pair production in association with a W or Z boson and measurements of top quark properties such as the spin correlation and W boson helicity in top quark pair events.
Estimating Cosmological Parameter Covariance
Taylor, Andy
2014-01-01
We investigate the bias and error in estimates of the cosmological parameter covariance matrix, due to sampling or modelling the data covariance matrix, for likelihood width and peak scatter estimators. We show that these estimators do not coincide unless the data covariance is exactly known. For sampled data covariances, with Gaussian distributed data and parameters, the parameter covariance matrix estimated from the width of the likelihood has a Wishart distribution, from which we derive the mean and covariance. This mean is biased and we propose an unbiased estimator of the parameter covariance matrix. Comparing our analytic results to a numerical Wishart sampler of the data covariance matrix we find excellent agreement. An accurate ansatz for the mean parameter covariance for the peak scatter estimator is found, and we fit its covariance to our numerical analysis. The mean is again biased and we propose an unbiased estimator for the peak parameter covariance. For sampled data covariances the width estimat...
Binding of Quarks and the $\\pi N$ $\\sigma$-term
Glozman, L Ya
1996-01-01
It is shown that the binding effect that is associated with the short range part of the Goldstone boson exchange interaction between constituent quarks provides a good description of the $\\pi N$ $\\sigma$-term.
Spectrum of heavy baryons in the quark model
Yoshida, Tetsuya; Hosaka, Atsushi; Oka, Makoto; Sadato, Katsunori
2015-01-01
Single- and double- heavy baryons are studied in the constituent quark model. The model Hamiltonian is chosen as a standard one with two exceptions : (1) The color-Coulomb term depend on quark masses, and (2) an antisymmetric $LS$ force is introduced. Model parameters are fixed by the strange baryon spectra, $\\Lambda$ and $\\Sigma$ baryons. The masses of the observed charmed and bottomed baryons are, then, fairly well reproduced. Our focus is on the low-lying negative-parity states, in which the heavy baryons show specific excitation modes reflecting the mass differences of heavy and light quarks. By changing quark masses from the SU(3) limit to the strange quark mass, further to the charm and bottom quark masses, we demonstrate that the spectra change from the SU(3) symmetry patterns to the heavy quark symmetry ones.
Contribution of Quark Structure Term in Nucleon Electric and Magnetic Form Factors
Institute of Scientific and Technical Information of China (English)
WANG Hong-Min; ZHANG Ben-Ai
2004-01-01
The constituent quarks in the nucleon have always been considered as a point-like particle in the relativistic constituent quark model. However its calculation results of GnE agree poorly with the new experimental data. The electromagnetic structure of light front constituent quarks is considered in this paper. We find that the calculation results have good agreement with the new experimental data of GnE after considering the contribution of the quark structure term. This treatment seems to be able to improve the fit to experimental data of Gep/GMp, /Q2F2p/kpF1p,and Gen/GMn as well.
Sun, Kai-Jia
2016-01-01
We study the production of $\\Lambda\\Lambda$ and $\\bar{\\Lambda \\text{n}}$ exotic states in central Pb+Pb collisions at $\\sqrt{s_{NN}}=2.76$ TeV via both hadron and quark coalescence within the covariant coalescence model with a blast-wave-like parametrization for the phase-space configurations of constituent particles at freezeout. In the hadron coalescence, the two states are considered as molecular states while they are considered as six-quark states in the quark coalescence. For $\\bar{\\Lambda \\text{n}}$, we find that the yields of both molecular and six-quark states are much larger than the experimental upper-limits. For $\\Lambda\\Lambda$, while the molecule-state yield is much larger than the experimental upper-limits, the six-quark-state yield could be lower than the upper-limits. The higher molecule-state yields are mainly due to the large contribution of strong resonance decays into nucleons and $\\Lambda$ which can significantly enhance the molecule-state yields via hadron coalescence. Our results sugges...
Niggli, Ernst; Egger, Marcel
2002-05-01
Elementary subcellular Ca2+ signals arising from the opening of single ion channels may offer the possibility to examine the stochastic behavior and the microscopic chemical reaction rates of these channel proteins in their natural environment. Such an analysis can yield detailed information about the molecular function that cannot be derived from recordings obtained from an ensemble of channels. In this review, we summarize experimental evidence suggesting that Ca2+ sparks, elementary Ca2+ signaling events of cardiac and skeletal muscle excitation contraction coupling, may be comprised of a number of smaller Ca2+ signaling events, the Ca2+ quarks.
Quark mass effects in quark number susceptibilities
Graf, Thorben
2016-01-01
The quark degrees of freedom of the QGP with special focus on mass effects are investigated. A next-to-leading-order perturbation theory approach with quark mass dependence is applied and compared to lattice QCD results.
Quark confinement and the fractional quantum Hall effect
Institute of Scientific and Technical Information of China (English)
WANG Hai-Jun; GENG Wen-Tong
2008-01-01
Working in the physics of Wilson factor and Aharonov-Bohm effect,we find in the fluxtubequark system the topology of a baryon consisting of three heavy flavor quarks resembles that of the fractional quantum Hall effect(FQHE)in condensed matter.This similarity yields the result that the constituent quarks of baryon have the"filling factor"1/3.thus the previous conjecture that quark confinement is a correlation effect is confirmed.Moreover,by deriving a Hamiltonian of the system analogous to that of FQHE,we predict an energy gap for the ground state of a heavy three-quark system.
Dynamically Running Mass of Light Quark and QCD Vacuum Condensates
Institute of Scientific and Technical Information of China (English)
ZHOULi-Juan; PINGRong-Gang
2004-01-01
Based on Dyson-Schwinger equations (DSEs) in “rainbow”approximation, the dynamically running mass of light quark and QCD vacuum condensate are investigated. The structure of non-local quark vacuum condensate, the values of local vacuum condensate of quarks and quark-gluon mixture, and dynamical transition of quark mass from current quark to constituent quark are illustrated. At the same time, according to the knowledge and experience learned from an extensive study of the solutions of DSEs， a parameterized form of confining quark propagator is suggested for a practical use. The new parameterized form of quark propagator is analytic everywhere in the finite complex p2-plane and has no Lehmann representation. The predictions for p2-dependence of effective quark masses, Mr(p2), defined by the self-energy functions Af(p2) and Bf(p2), both from the numerical solutions of DSEs and from its parameterized form, are shown dynamically. Our conclusion is that all numerical results are consistent with empirical values used in(QCD sum rules and lattice QCD calculations. For a qualitative study, the parameterized form is a sumciently good approximation to confining quark propagator.
Dynamically Running Mass of Light Quark and QCD Vacuum Condensates
Institute of Scientific and Technical Information of China (English)
ZHOU Li-Juan; PING Rong-Gang; MA Wei-Xing
2004-01-01
Based on Dyson-Schwinger equations (DSEs) in "rainbow" approximation, the dynamically running mass of light quark and QCD vacuum condensate are investigated. The structure of non-local quark vacuum condensate, the values of local vacuum condensate of quarks and quark-gluon mixture, and dynamical transition of quark mass from current quark to constituent quark are illustrated. At the same time, according to the knowledge and experience learned from an extensive study of the solutions of DSEs, a parameterized form of confining quark propagator is suggested for a practical use. The new parameterized form of quark propagator is analytic everywhere in the finite complex p2-plane and has no Lehmann representation. The predictions for p2-dependence of effective quark masses, Mf(p2), defined by the self-energy functions Af(p2) and Bf(p2), both from the numerical solutions of DSEs and from its parameterized form, are shown dynamically. Our conclusion is that all numerical results are consistent with empirical values used in QCD sum rules and lattice QCD calculations. For a qualitative study, the parameterized form is a sufficiently good approximation to confining quark propagator.
Quark-Quark Forces in Quantum Chromodynamics
Arkhipov, A A
2014-01-01
By single-time reduction technique of Bethe-Salpeter formalism for two-fermion systems analytical expressions for the quasipotential of quark-quark interactions in QCD have been obtained in one-gluon exchange approximation. The influence of infrared singularities of gluon Green`s functions on the character of quark-quark forces in QCD has been investigated. The way the asymptotic freedom manifests itself in terms of two-quark interaction quasipotential in quantum chromodynamics is shown. Consistent relativistic consideration of quark interaction problem by single-time reduction technique in QFT allows one to establish a nontrivial energy dependence of the two-quark interaction quasipotential. As a result of the energy dependence of the interaction quasipotential, the character of the forces changes qualitatively during the transition from the discrete spectrum (the region of the negative values of the binding energy) to the continuous spectrum (that of the positive values of the binding energy): the smooth be...
Black, Kevin; The ATLAS collaboration
2017-01-01
The top quark is the heaviest known fundamental particle. As it is the only quark that decays before it hadronizes, this gives us the unique opportunity to probe the properties of bare quarks at the Large Hadron Collider. This talk will present highlights of a few recent precision measurements by the ATLAS Collaboration of the top quark using 13 TeV and 8 TeV collision data: top-quark pair and single top production cross sections including differential distributions will be presented alongside top quark properties measurements. These measurements, including results using boosted top quarks, probe our understanding of top quark production in the TeV regime. Measurements of the top quark mass and searches for rare top quark decays are also presented.
Manifestly covariant electromagnetism
Energy Technology Data Exchange (ETDEWEB)
Hillion, P. [Institut Henri Poincare' , Le Vesinet (France)
1999-03-01
The conventional relativistic formulation of electromagnetism is covariant under the full Lorentz group. But relativity requires covariance only under the proper Lorentz group and the authors present here the formalism covariant under the complex rotation group isomorphic to the proper Lorentz group. The authors discuss successively Maxwell's equations, constitutive relations and potential functions. A comparison is made with the usual formulation.
Sharma, A
1997-01-01
A qqq BSE formalism based on an input 4-fermion Lagrangian of "current" u,d quarks, is employed for the construction of a relativistic qqq-wave function) via the BSE. Chiral invariance is ensured by the vector character of the gluonic propagator in the infrared regime, while the `constituent' masses are the low momentum limits of the dynamicalmass function generated by standard DB{\\chi}. The Covariant Instantaneity Ansatz (CIA) gives an exact 3D reduction of the BSE for baryon spectroscopy, while the reconstructed 4D form identifies the baryon quark vertex function reconstructed through a reversal of steps offered by the CIA structure. It is employed for the quark loop integrals for the neutron - proton mass difference which receives contributions from two sources : i) the strong SU(2) effect arising from the $u-d$ mass difference (4 MeV); ii) the e.m. effect of the respective quark charges. The resultant n-p difference works out at 1.28 MeV (vs. 1.29 expt), with only two free parameters characterizing the in...
Octet baryon electromagnetic form factors in a relativistic quark model
Ramalho, G
2011-01-01
We study the octet baryon electromagnetic properties by applying the covariant spectator quark model, and provide covariant parametrization that can be used to study baryon electromagnetic reactions. While we use the lattice QCD data in the large pion mass regime (small pion cloud effects) to determine the parameters of the model in the valence quark sector, we use the nucleon physical and octet baryon magnetic moment data to parameterize the pion cloud contributions. The valence quark contributions for the octet baryon electromagnetic form factors are estimated by extrapolating the lattice parametrization in the large pion mass regime to the physical regime. As for the pion cloud contributions, we parameterize them in a covariant, phenomenological manner, combined with SU(3) symmetry. We also discuss the impact of the pion cloud effects on the octet baryon electromagnetic form factors and their radii.
Octet Baryon Electromagnetic Form Factors in a Relativistic Quark Model
Energy Technology Data Exchange (ETDEWEB)
Gilberto Ramalho, Kazuo Tsushima
2011-09-01
We study the octet baryon electromagnetic properties by applying the covariant spectator quark model, and provide covariant parametrization that can be used to study baryon electromagnetic reactions. While we use the lattice QCD data in the large pion mass regime (small pion cloud effects) to determine the parameters of the model in the valence quark sector, we use the nucleon physical and octet baryon magnetic moment data to parameterize the pion cloud contributions. The valence quark contributions for the octet baryon electromagnetic form factors are estimated by extrapolating the lattice parametrization in the large pion mass regime to the physical regime. As for the pion cloud contributions, we parameterize them in a covariant, phenomenological manner, combined with SU(3) symmetry. We also discuss the impact of the pion cloud effects on the octet baryon electromagnetic form factors and their radii.
On the strange quark mass with improved staggered quarks
Hein, J.; Davies, C.; Lepage, G. P.; Mason, Q.; Trottier, H.
2002-01-01
We present results on the sum of the masses of light and strange quark using improved staggered quarks. Our calculation uses 2+1 flavours of dynamical quarks. The effects of the dynamical quarks are clearly visible.
Effective field theories of baryons and mesons, or, what do quarks do?
Energy Technology Data Exchange (ETDEWEB)
Keaton, G.L. [Lawrence Berkeley Lab., CA (United States). Theoretical Physics Group
1995-06-26
This thesis is an attempt to understand the properties of the protons, pions and other hadrons in terms of their fundamental building blocks. In the first chapter the author reviews several of the approaches that have already been developed. The Nambu-Jona-Lasinio model offers the classic example of a derivation of meson properties from a quark Lagrangian. The chiral quark model encodes much of the intuition acquired in recent decades. The author also discusses the non-linear sigma model, the Skyrme model, and the constituent quark model, which is one of the oldest and most successful models. In the constituent quark model, the constituent quark appears to be different from the current quark that appears in the fundamental QCD Lagrangian. Recently it was proposed that the constituent quark is a topological soliton. In chapter 2 the author investigates this soliton, calculating its mass, radius, magnetic moment, color magnetic moment, and spin structure function. Within the approximations used, the magnetic moments and spin structure function cannot simultaneously be made to agree with the constituent quark model. In chapter 3 the author uses a different plan of attack. Rather than trying to model the constituents of the baryon, he begins with an effective field theory of baryons and mesons, with couplings and masses that are simply determined phenomenologically. Meson loop corrections to baryon axial currents are then computed in the 1/N expansion. It is already known that the one-loop corrections are suppressed by a factor 1/N; here it is shown that the two-loop corrections are suppressed by 1/N{sup 2}. To leading order, these corrections are exactly the same as would be calculated in the constituent quark model. This method therefore offers a different approach to the constituent quark.
Indian Academy of Sciences (India)
Yuji Takeuchi
2012-10-01
Since the top quark was discovered at Tevatron in 1995, many top quark properties have been measured. However, the top quark is still interesting due to unique features which originate from the extremely heavy mass, and providing various test grounds on the Standard Model as well as searches for a new physics. Though the measurements of the top quark had been performed only at Tevatron so far, LHC is now ready for measurements with more top quarks than Tevatron. In this article, recent measurements of top quark properties from Tevatron (CDF and DØ) as well as LHC (ATLAS and CMS) are presented.
Nucleon electromagnetic form factors from the covariant Faddeev equation
Eichmann, G.
2011-07-01
We compute the electromagnetic form factors of the nucleon in the Poincaré-covariant Faddeev framework based on the Dyson-Schwinger equations of QCD. The general expression for a baryon’s electromagnetic current in terms of three interacting dressed quarks is derived. Upon employing a rainbow-ladder gluon-exchange kernel for the quark-quark interaction, the nucleon’s Faddeev amplitude and electromagnetic form factors are computed without any further truncations or model assumptions. The form-factor results show clear evidence of missing pion-cloud effects below a photon momentum transfer of ˜2GeV2 and in the chiral region, whereas they agree well with experimental data at higher photon momenta. Thus, the approach reflects the properties of the nucleon’s quark core.
Electromagnetic baryon form factors in the Poincaré-covariant Faddeev approach
Energy Technology Data Exchange (ETDEWEB)
Alkofer, Reinhard, E-mail: reinhard.alkofer@uni-graz.at [Institute of Physics, University of Graz (Austria); Eichmann, Gernot; Sanchis-Alepuz, Hèlios; Williams, Richard [Institute of Theoretical Physics I, Justus-Liebig-Universität Giessen (Germany)
2015-08-15
Baryons are treated as three-quark systems using QCD degrees of freedom in Poincaré-covariant bound-state equations. The quark self-energy as well as the interaction between quarks are approximated by a vector-vector interaction via a single dressed-gluon exchange (rainbow-ladder truncation), thereby allowing a unified study of quark, meson and baryon properties. Here we will focus on the calculation of electromagnetic properties of spin-1/2 and spin-3/2 ground state baryons.
Estimating transport coefficients in hot and dense quark matter
Deb, Paramita; Mishra, Hiranmaya
2016-01-01
We compute the transport coefficients-- namely, coefficients of shear and bulk viscosity as well as thermal conductivity for hot and dense quark matter. The calculations are performed within the Nambu Jona Lasinio (NJL) model. The estimation of the transport coefficients is made using a quasi particle approach of solving Boltzmann kinetic equation within the relaxation time approximation. The transition rates are calculated in a manifestly covariant manner to estimate the thermal averaged cross sections for quark quark as well as quark anti-quark scattering. The calculations are performed for finite chemical potential also. Within the parameters of the model, the ratio of shear viscosity to entropy density has a minimum at the Mott transition temperature. At vanishing chemical potential, the ratio of bulk viscosity to entropy density, on the other hand, decrease with temperature with a sharp decrease near the critical temperature and vanishes beyond it. At finite chemical potential, however, it increases slow...
Covariant Hamiltonian field theory
Giachetta, G; Sardanashvily, G
1999-01-01
We study the relationship between the equations of first order Lagrangian field theory on fiber bundles and the covariant Hamilton equations on the finite-dimensional polysymplectic phase space of covariant Hamiltonian field theory. The main peculiarity of these Hamilton equations lies in the fact that, for degenerate systems, they contain additional gauge fixing conditions. We develop the BRST extension of the covariant Hamiltonian formalism, characterized by a Lie superalgebra of BRST and anti-BRST symmetries.
Institute of Scientific and Technical Information of China (English)
ZONG Hong-Shi; WU Xiao-Hua; SUN Wei-Min; ZHAO En-Guang; WANG Fan
2003-01-01
A method for obtaining the smallcurrent quark mass dependence of the dressed quark propagator froman effective quark-quark interaction model is developed. Within this approach the small current quark mass effects ondressed-quark propagator have been studied. A comparison with previous results is given.
Energy Technology Data Exchange (ETDEWEB)
Paschos, E A
1976-01-01
This contribution reviews the evidence accumulated over the past year in favor of quarks and partons. Then it applies the quark ideas in order to interpret the neutrino-induced production of charm and the structure of neutral currents.
Pion production model - connection between dynamics and quark models
Energy Technology Data Exchange (ETDEWEB)
Lee, T.-S. H.; Sato, T.
2000-05-17
The authors discuss the difficulties in testing the hadron models by using the N{sup *} parameters extracted from the empirical amplitude analyses of the {pi}N and {gamma}N reaction data. As an alternative or perhaps a more advantageous approach, they present a Hamiltonian formulation that can relate the pion production dynamics and the constituent quark models of N{sup *} structure. The application of the approach in investigating the {Delta} and N{sup *}(S{sub 11}) excitations is reviewed. It is found that while the {Delta} excitation can be described satisfactory, the {pi}N scattering in S{sub 11} channel can not be described by the constituent quark models based on either the one-gluon-exchange or one-meson-exchange mechanisms. A phenomenological quark-quark potential has been constructed to reproduce the S{sub 11} amplitude.
Iorio, Alberto Orso Maria
2016-01-01
Measurements of top quarks from Run-I and Run-II of the LHC are presented. Results on dif- ferential and inclusive top quark production cross sections, measured by the ATLAS, CMS and LHCb experiments, and measurements of top quark properties and mass are reported.
ATLAS collaboration; LHCb collaboration
2016-01-01
Measurements of top quarks from Run-I and Run-II of the LHC are presented. Results on differential and inclusive top quark production cross sections, measured by the ATLAS, CMS and LHCb experiments, and measurements of top quark properties and mass are reported.
Bergshoeff, E.; Pope, C.N.; Stelle, K.S.
1990-01-01
We discuss the notion of higher-spin covariance in w∞ gravity. We show how a recently proposed covariant w∞ gravity action can be obtained from non-chiral w∞ gravity by making field redefinitions that introduce new gauge-field components with corresponding new gauge transformations.
Penta-Quark States with Strangeness, Hidden Charm and Beauty
Wu, Jia-Jun; Zou, Bing-Song
The classical quenched quark models with three constituent quarks provide a good description for the baryon spatial ground states, but fail to reproduce the spectrum of baryon excited states. More and more evidences suggest that unquenched effects with multi-quark dynamics are necessary ingredients to solve the problem. Several new hyperon resonances reported recently could fit in the picture of penta-quark states. Based on this picture, some new hyperon excited states were predicted to exist; meanwhile with extension from strangeness to charm and beauty, super-heavy narrow N* and Λ* resonances with hidden charm or beauty were predicted to be around 4.3 and 11 GeV, respectively. Recently, two of such N* with hidden charm might have been observed by the LHCb experiment. More of those states are expected to be observed in near future. This opens a new window in order to study hadronic dynamics for the multi-quark states.
Penta-quark States with Strangeness, Hidden Charm and Beauty
Wu, Jia-Jun
2015-01-01
The classical quenched quark models with three constituent quarks provide a good description for the baryon spatial ground states, but fail to reproduce the spectrum of baryon excited states. More and more evidences suggest that unquenched effects with multi-quark dynamics are necessary ingredients to solve the problem. Several new hyperon resonances reported recently could fit in the picture of penta-quark states. Based on this picture, some new hyperon excited states were predicted to exist; meanwhile with extension from strangeness to charm and beauty, super-heavy narrow $N^*$ and $\\Lambda^*$ resonances with hidden charm or beauty were predicted to be around 4.3 and 11 GeV, respectively. Recently, two of such $N^*$ with hidden charm might have been observed by the LHCb experiment. More of those states are expected to be observed in near future. This opens a new window in order to study hadronic dynamics for the multi-quark states.
Searches for baryons with multiple heavy quarks at LHCb
CERN. Geneva
2017-01-01
Hadrons are systems bound by the strong interaction, which is described at the fundamental level by quantum chromodynamics (QCD). While QCD is well understood at high energy in the perturbative regime, low-energy phenomena, such as the binding of quarks and gluons within hadrons, are more difficult to predict. High precision measurements are then of paramount importance to test the reliability of several models and computational techniques, such as constituent-quark models or lattice-QCD calculations, in predicting the mass spectrum and the properties of hadrons. Owing to its excellent capabilities with particle identification, tracking and vertex reconstruction, LHCb is in a unique position to make significant contributions to the sector of particle spectroscopy. For example, five narrow structures have been recently observed in the $\\Xi_c^+K^-$ mass spectrum, consistent with excited $\\Omega_c^{0}$ states, composed of a charm quark and two strange quarks. Despite the fact that the quark model predicts the ex...
Strange baryon spectroscopy in the relativistic quark model
Faustov, R N
2015-01-01
Mass spectra of strange baryons are calculated in the framework of the relativistic quark model based on the quasipotential approach. Baryons are treated as the relativistic quark-diquark bound systems. It is assumed that two quarks with equal constituent masses form a diquark. The diquark excitations and its internal structure are consistently taken into account. Calculations are performed up to rather high orbital and radial excitations of strange baryons. On this basis the Regge trajectories are constructed. The obtained results are compared with available experimental data and previous predictions. It is found that all masses of the 4- and 3-star, as well as most of the 2- and 1-star states of strange baryons with established quantum numbers are well reproduced. The developed relativistic quark-diquark model predicts less excited states than three-quark models of strange baryons.
Strange baryon spectroscopy in the relativistic quark model
Faustov, R. N.; Galkin, V. O.
2015-09-01
Mass spectra of strange baryons are calculated in the framework of the relativistic quark model based on the quasipotential approach. Baryons are treated as relativistic quark-diquark bound systems. It is assumed that two quarks with equal constituent masses form a diquark. The diquark excitations and its internal structure are consistently taken into account. Calculations are performed up to rather high orbital and radial excitations of strange baryons. On this basis the Regge trajectories are constructed. The obtained results are compared with available experimental data and previous predictions. It is found that all masses of the 4- and 3-star states of strange baryons with established quantum numbers, as well as most of the 2- and 1-star states, are well reproduced. The developed relativistic quark-diquark model predicts less excited states than three-quark models of strange baryons.
Meson Spectroscopy in the Light Quark Sector
Energy Technology Data Exchange (ETDEWEB)
De Vita, R.; Lunardi, S.; Bizzeti, P. G.; Bucci, C.; Chiari, M.; Dainese, A.; Di Nezza, P.; Menegazzo, R.; Nannini, A.; Signorini, C.; Valiente-Dobon, J. J.
2014-01-01
Understanding the hadron spectrum is one of the fundamental issues in modern particle physics. We know that existing hadron configurations include baryons, made of three quarks, and mesons, made of quark-antiquark pairs. However most of the mass of the hadrons is not due to the mass of these elementary constituents but to their binding force. Studying the hadron spectrum is therefore a tool to understand one of the fundamental forces in nature, the strong force, and Quantum Chromo Dynamics (QCD), the theory that describes it. This investigation can provide an answer to fundamental questions as what is the origin of the mass of hadrons, what is the origin of quark confinement, what are the relevant degrees of freedom to describe these complex systems and how the transition between the elementary constituents, quarks and gluons, and baryons and mesons occurs. In this field a key tool is given by meson spectroscopy. Mesons, being made by a quark and an anti-quark, are the simplest quark bound system and therefore the ideal benchmark to study the interaction between quarks and understand what the role of gluons is. In this investigation, it is fundamental to precisely determine the spectrum and properties of mesons but also to search for possible unconventional states beyond the configuration q{anti q} as tetraquarks (qq{anti qq}), hybrids (q{anti q}g) and glueballs. These states can be distinguished unambiguously from regular mesons when they have exotic quantum numbers, i.e. combinations of total angular momentum, spin and parity that are not allowed for q{anti q} states. These are called exotic quantum numbers and the corresponding states are referred to as exotics. The study of the meson spectrum and the search for exotics is among the goals of several experiments in the world that exploit different reaction processes, as e{sup +}e{sup -} annihilation, p{anti p} annihilation, pion scattering, proton-proton scattering and photo-production, to produce meson states
The mass effect of the quark phase transition in supernova core
Institute of Scientific and Technical Information of China (English)
Lai Xiang-Jun; Liu Men-Quan; Liu Jing-Jing; Luo Zhi-Quan
2008-01-01
Constituent quark mass model is adopted as a tentative one to study the phase transition between two-flavour quark matter and more stable thres-flavour quark matter in the core of supernovae.The result shows that the transition has a significant influence on the increasing of the core temperature,the neutrino abundance and the neutrino energies,which contributes to the enhancement of the successful probability of supernova explosion.However,the equilibrium values of these parameters (except the temperature) from the constituent quark mass model in this work are slightly bigger than those obtained from the other model.And we find that the constituent quark mass model is also applicable to describing the transition in the supernova core.
Nonlocal quark model description of a composite Higgs particle
Kachanovich, Aliaksei
2016-01-01
We propose a description of the Higgs boson as top-antitop quark bound state within a nonlocal relativistic quark model of Nambu - Jona-Lasinio type. In contrast to model with local four-fermion interaction, the mass of the scalar bound state can be lighter than the sum of its constituents. This is achieved by adjusting the interaction range and the value of the coupling constant to experimental data, for both the top quark mass and the scalar Higgs boson mass, which can simultaneously be described.
Quark Mass Dependence of Nucleon Magnetic Moment and Charge Radii
Institute of Scientific and Technical Information of China (English)
MA Wei-Xing; ZHOU Li-Juan; GU Yun-Ting; PING Rong-Gang
2005-01-01
Understanding hadron structure within the framework of QCD is an extremely challenging problem. Our purpose here is to explain the model-independent consequences of the approximated chiral symmetry of QCD for two famous results concerning the quark structure of the nucleon. We show that both the apparent success of the constituent quark model in reproducing the ratio of proton to neutron magnetic moments and the apparent success of the Foldy term in reproducing the observed charge radius of the neutron are coincidental. That is, a relatively small change of the current quark mass would spoil both results.
Space-Time Geometry of Quark and Strange Quark Matter
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
We study quark and strange quark matter in the context of general relativity. For this purpose, we solve Einstein's field equations for quark and strange quark matter in spherical symmetric space-times. We analyze strange quark matter for the different equations of state (EOS) in the spherical symmetric space-times, thus we are able to obtain the space-time geometries of quark and strange quark matter. Also, we discuss die features of the obtained solutions. The obtained solutions are consistent with the results of Brookhaven Laboratory, i.e. the quark-gluon plasma has a vanishing shear (i.e. quark-gluon plasma is perfect).
The quark-gluon vertex in Landau gauge bound-state studies
Williams, Richard
2015-05-01
We present a practical method for the solution of the quark-gluon vertex for use in Bethe-Salpeter and Dyson-Schwinger calculations. The efficient decomposition into the necessary covariants is detailed, with the numerical algorithm outlined for both real and complex Euclidean momenta. A truncation of the quark-gluon vertex, that neglects explicit back-coupling to enable the application to bound-state calculations, is given together with results for the quark propagator and quark-gluon vertex for different quark flavours. The relative impact of the various components of the quark-gluon vertex is highlighted with the flavour dependence of the effective quark-gluon interaction obtained, thus providing insight for the construction of phenomenological models within the rainbow ladder. Finally, we solve the corresponding Green's functions for complex Euclidean momenta as required in future bound-state calculations.
The quark-gluon vertex in Landau gauge bound-state studies
Energy Technology Data Exchange (ETDEWEB)
Williams, Richard [Justus-Liebig University of Giessen, Institute of Theoretical Physics, Giessen (Germany)
2015-05-15
We present a practical method for the solution of the quark-gluon vertex for use in Bethe-Salpeter and Dyson-Schwinger calculations. The efficient decomposition into the necessary covariants is detailed, with the numerical algorithm outlined for both real and complex Euclidean momenta. A truncation of the quark-gluon vertex, that neglects explicit back-coupling to enable the application to bound-state calculations, is given together with results for the quark propagator and quark-gluon vertex for different quark flavours. The relative impact of the various components of the quark-gluon vertex is highlighted with the flavour dependence of the effective quark-gluon interaction obtained, thus providing insight for the construction of phenomenological models within the rainbow ladder. Finally, we solve the corresponding Green's functions for complex Euclidean momenta as required in future bound-state calculations. (orig.)
Nucleon Structure Function F2 in the Resonance Region and Quark-Hadron Duality
Institute of Scientific and Technical Information of China (English)
DONG Yu-Bing; LI Ming-Fei
2003-01-01
Based on a simple nonrelativistic constituent quark model, the nucleon structure function F2 in theresonance region is estimated by taking the contributions from low-lying nucleon resonances into account. Calculatedresults are employed to study quark-hardon duality in the nucleon electron scattering process by comparing them to thescaling behavior from the data in deep inelastic scattering region.
Energy Technology Data Exchange (ETDEWEB)
Ahmadov, A.; Azuelos, G.; Bauer, U.; Belyaev, A.; Berger, E. L.; Sullivan, Z.; Tait, T. M. P.
2000-03-24
The top quark, when it was finally discovered at Fermilab in 1995 completed the three-generation structure of the Standard Model (SM) and opened up the new field of top quark physics. Viewed as just another SM quark, the top quark appears to be a rather uninteresting species. Produced predominantly, in hadron-hadron collisions, through strong interactions, it decays rapidly without forming hadrons, and almost exclusively through the single mode t {r_arrow} Wb. The relevant CKM coupling V{sub tb} is already determined by the (three-generation) unitarity of the CKM matrix. Rare decays and CP violation are unmeasurable small in the SM. Yet the top quark is distinguished by its large mass, about 35 times larger than the mass of the next heavy quark, and intriguingly close to the scale of electroweak (EW) symmetry breaking. This unique property raises a number of interesting questions. Is the top quark mass generated by the Higgs mechanism as the SM predicts and is its mass related to the top-Higgs-Yukawa coupling? Or does it play an even more fundamental role in the EW symmetry breaking mechanism? If there are new particles lighter than the top quark, does the top quark decay into them? Could non-SM physics first manifest itself in non-standard couplings of the top quark which show up as anomalies in top quark production and decays? Top quark physics tries to answer these questions. Several properties of the top quark have already been examined at the Tevatron. These include studies of the kinematical properties of top production, the measurements of the top mass, of the top production cross-section, the reconstruction of t{bar t}pairs in the fully hadronic final states, the study of {tau} decays of the top quark, the reconstruction of hadronic decays of the W boson from top decays, the search for flavor changing neutral current decays, the measurement of the W helicity in top decays, and bounds on t{bar t} spin correlations. Most of these measurements are limited by
Testa, Massimo
1990-01-01
In the large quark mass limit, an argument which identifies the mass of the heavy-light pseudoscalar or scalar bound state with the renormalized mass of the heavy quark is given. The following equation is discussed: m(sub Q) = m(sub B), where m(sub Q) and m(sub B) are respectively the mass of the heavy quark and the mass of the pseudoscalar bound state.
Juste, A
2006-01-01
Ten years after its discovery at the Tevatron collider, we still know little about the top quark. Its large mass suggests it may play a key role in the mechanism of Electroweak Symmetry Breaking (EWSB), or open a window of sensitivity to new physics related to EWSB and preferentially coupled to it. To determine whether this is the case, precision measurements of top quark properties are necessary. The high statistics samples being collected by the Tevatron experiments during Run II start to incisively probe the top quark sector. This report summarizes the experimental status of the top quark, focusing in particular on the recent measurements from the Tevatron Run II.
Cuevas Maestro, Javier
2016-01-01
An overview of recent top quark measurements in proton-proton collisions at 7, and 8 TeV in data collected with the CMS and ATLAS experiments at the LHC, using a data sample collected during the years 2011, 2012 is presented. The results include measurements of top-quark pairs spin correlation, the top pair charge asymmetry, the cross section of top-quark pair events produced in association with a W or a Z boson. The mass of the top quark is estimated by different methods. Some results on the same topics are also presented in data collected by the CDF and D0 collaborations at the Tevatron collider.
Ghosh, Sabyasachi; Roy, Victor; Serna, Fernando E; Krein, Gastão
2015-01-01
We have calculated the temperature dependence of shear $\\eta$ and bulk $\\zeta$ viscosities of quark matter due to quark-meson fluctuations. The quark thermal width originating from quantum fluctuations of quark-$\\pi$ and quark-$\\sigma$ loops at finite temperature is calculated with the formalism of real-time thermal field theory. Temperature-dependent constituent-quark and meson masses, and quark-meson couplings are obtained in the Nambu--Jona-Lasinio model. We found a non-trivial influence of the temperature-dependent masses and couplings on the Landau-cut structure of the quark self-energy. Our results for the ratios $\\eta/s$ and $\\zeta/s$, where $s$ is the entropy density (also determined in the Nambu--Jona-Lasinio model in the quasi-particle approximation), are in fair agreement with results of the literature obtained from different models and techniques. In particular, our result for $\\eta/s$ has a minimum very close to the conjectured AdS/CFT lower bound, $\\eta/s = 1/4\\pi$.
Ghosh, Sabyasachi; Peixoto, Thiago C.; Roy, Victor; Serna, Fernando E.; Krein, Gastão
2016-04-01
We have calculated the temperature dependence of shear η and bulk ζ viscosities of quark matter due to quark-meson fluctuations. The quark thermal width originating from quantum fluctuations of quark-π and quark-σ loops at finite temperature is calculated with the formalism of real-time thermal field theory. Temperature-dependent constituent-quark and meson masses and quark-meson couplings are obtained in the Nambu-Jona-Lasinio model. We found a nontrivial influence of the temperature-dependent masses and couplings on the Landau-cut structure of the quark self-energy. Our results for the ratios η /s and ζ /s , where s is the entropy density (also determined in the Nambu-Jona-Lasinio model in the quasiparticle approximation), are in fair agreement with results of the literature obtained from different models and techniques. In particular, our result for η /s has a minimum very close to the quantum lower bound, η /s =1 /4 π .
New quarks: exotic versus strong
Holdom, B.
2011-01-01
The new quarks of a fourth family are being pushed into the strongly interacting regime due to the lower limits on their masses. The theoretical basis and experimental implications of such quarks are compared with exotic quarks.
Dakin, James T.
1974-01-01
Reviews theoretical principles underlying the quark model. Indicates that the agreement with experimental results and the understanding of the quark-quark force are two hurdles for the model to survive in the future. (CC)
Dakin, James T.
1974-01-01
Reviews theoretical principles underlying the quark model. Indicates that the agreement with experimental results and the understanding of the quark-quark force are two hurdles for the model to survive in the future. (CC)
Quark mass functions and pion structure in Minkowski space
Energy Technology Data Exchange (ETDEWEB)
Biernat, Elmer P. [CFTP, Institute Superior Tecnico; Gross, Franz L. [JLAB; Pena, Maria Teresa [CFTP, Institute Superior Tecnico; Stadler, Alfred [University of Evora
2014-03-01
We present a study of the dressed quark mass function and the pion structure in Minkowski space using the Covariant Spectator Theory (CST). The quark propagators are dressed with the same kernel that describes the interaction between different quarks. We use an interaction kernel in momentum space that is a relativistic generalization of the linear confining q-qbar potential and a constant potential shift that defines the energy scale. The confining interaction has a Lorentz scalar part that is not chirally invariant by itself but decouples from the equations in the chiral limit and therefore allows the Nambu--Jona-Lasinio (NJL) mechanism to work. We adjust the parameters of our quark mass function calculated in Minkowski-space to agree with LQCD data obtained in Euclidean space. Results of a calculation of the pion electromagnetic form factor in the relativistic impulse approximation using the same mass function are presented and compared with experimental data.
A covariant model for the $\\gamma^\\ast N \\to N^\\ast(1520)$ reaction
Ramalho, G
2014-01-01
We apply the covariant spectator quark model to the study of the electromagnetic structure of the $N^\\ast(1520)$ state ($J^{P}= \\frac{3}{2}^-$), an important resonance from the second resonance region in both spacelike and timelike regimes. The contributions from the valence quark effects are calculated for the $\\gamma^\\ast N \\to N^\\ast(1520)$ helicity amplitudes. The results are used to parametrize the meson cloud dominant at low $Q^2$.
Frasinski, Leszek J.
2016-08-01
Recent technological advances in the generation of intense femtosecond pulses have made covariance mapping an attractive analytical technique. The laser pulses available are so intense that often thousands of ionisation and Coulomb explosion events will occur within each pulse. To understand the physics of these processes the photoelectrons and photoions need to be correlated, and covariance mapping is well suited for operating at the high counting rates of these laser sources. Partial covariance is particularly useful in experiments with x-ray free electron lasers, because it is capable of suppressing pulse fluctuation effects. A variety of covariance mapping methods is described: simple, partial (single- and multi-parameter), sliced, contingent and multi-dimensional. The relationship to coincidence techniques is discussed. Covariance mapping has been used in many areas of science and technology: inner-shell excitation and Auger decay, multiphoton and multielectron ionisation, time-of-flight and angle-resolved spectrometry, infrared spectroscopy, nuclear magnetic resonance imaging, stimulated Raman scattering, directional gamma ray sensing, welding diagnostics and brain connectivity studies (connectomics). This review gives practical advice for implementing the technique and interpreting the results, including its limitations and instrumental constraints. It also summarises recent theoretical studies, highlights unsolved problems and outlines a personal view on the most promising research directions.
Covariant Bardeen perturbation formalism
Vitenti, S. D. P.; Falciano, F. T.; Pinto-Neto, N.
2014-05-01
In a previous work we obtained a set of necessary conditions for the linear approximation in cosmology. Here we discuss the relations of this approach with the so-called covariant perturbations. It is often argued in the literature that one of the main advantages of the covariant approach to describe cosmological perturbations is that the Bardeen formalism is coordinate dependent. In this paper we will reformulate the Bardeen approach in a completely covariant manner. For that, we introduce the notion of pure and mixed tensors, which yields an adequate language to treat both perturbative approaches in a common framework. We then stress that in the referred covariant approach, one necessarily introduces an additional hypersurface choice to the problem. Using our mixed and pure tensors approach, we are able to construct a one-to-one map relating the usual gauge dependence of the Bardeen formalism with the hypersurface dependence inherent to the covariant approach. Finally, through the use of this map, we define full nonlinear tensors that at first order correspond to the three known gauge invariant variables Φ, Ψ and Ξ, which are simultaneously foliation and gauge invariant. We then stress that the use of the proposed mixed tensors allows one to construct simultaneously gauge and hypersurface invariant variables at any order.
The quark mean field model with pion and gluon corrections
Xing, Xueyong; Shen, Hong
2016-01-01
The properties of nuclear matter and finite nuclei are studied within the quark mean field (QMF) model by taking the effects of pion and gluon into account at the quark level. The nucleon is described as the combination of three constituent quarks confined by a harmonic oscillator potential. To satisfy the spirit of QCD theory, the contributions of pion and gluon on the nucleon structure are treated in second-order perturbation theory. For the nuclear many-body system, nucleons interact with each other by exchanging mesons between quarks. With different constituent quark mass, $m_q$, we determine three parameter sets about the coupling constants between mesons and quarks, named as QMF-NK1, QMF-NK2, and QMF-NK3 by fitting the ground-state properties of several closed-shell nuclei. It is found that all of the three parameter sets can give satisfactory description on properties of nuclear matter and finite nuclei, meanwhile they can also predict the larger neutron star mass around $2.3M_\\odot$ without the hypero...
Quark mean field model with pion and gluon corrections
Xing, Xueyong; Hu, Jinniu; Shen, Hong
2016-10-01
The properties of nuclear matter and finite nuclei are studied within the quark mean field (QMF) model by taking the effects of pions and gluons into account at the quark level. The nucleon is described as the combination of three constituent quarks confined by a harmonic oscillator potential. To satisfy the spirit of QCD theory, the contributions of pions and gluons on the nucleon structure are treated in second-order perturbation theory. In a nuclear many-body system, nucleons interact with each other by exchanging mesons between quarks. With different constituent quark mass, mq, we determine three parameter sets for the coupling constants between mesons and quarks, named QMF-NK1, QMF-NK2, and QMF-NK3, by fitting the ground-state properties of several closed-shell nuclei. It is found that all of the three parameter sets can give a satisfactory description of properties of nuclear matter and finite nuclei, moreover they also predict a larger neutron star mass around 2.3 M⊙ without hyperon degrees of freedom.
Contribution of Quark Structure Term in Nucleon Electric and Magnetic Form Factors
Institute of Scientific and Technical Information of China (English)
WANGHong-Min; ZHANGBen-Ai
2004-01-01
The constituent quarks in the nucleon have always been considered as a point-like particle in the relativisticconstituent quark model. However its calculation results of GEn agree poorly with the new experimental data. Theelectromagnetic structure of light front constituent quarks is considered in this paper. We find that the calculationresults have good agreement with the new experimental data of GEn after considering the contribution of the quarkstructure term. This treatment seems to be able to improve the fit to experimental data of GEp/GMp,√Q2F2p/kpF1p,and GEn/GMn as well.
Covariant canonical quantization
Energy Technology Data Exchange (ETDEWEB)
Hippel, G.M. von [University of Regina, Department of Physics, Regina, Saskatchewan (Canada); Wohlfarth, M.N.R. [Universitaet Hamburg, Institut fuer Theoretische Physik, Hamburg (Germany)
2006-09-15
We present a manifestly covariant quantization procedure based on the de Donder-Weyl Hamiltonian formulation of classical field theory. This procedure agrees with conventional canonical quantization only if the parameter space is d=1 dimensional time. In d>1 quantization requires a fundamental length scale, and any bosonic field generates a spinorial wave function, leading to the purely quantum-theoretical emergence of spinors as a byproduct. We provide a probabilistic interpretation of the wave functions for the fields, and we apply the formalism to a number of simple examples. These show that covariant canonical quantization produces both the Klein-Gordon and the Dirac equation, while also predicting the existence of discrete towers of identically charged fermions with different masses. Covariant canonical quantization can thus be understood as a ''first'' or pre-quantization within the framework of conventional QFT. (orig.)
Covariant canonical quantization
Von Hippel, G M; Hippel, Georg M. von; Wohlfarth, Mattias N.R.
2006-01-01
We present a manifestly covariant quantization procedure based on the de Donder-Weyl Hamiltonian formulation of classical field theory. Covariant canonical quantization agrees with conventional canonical quantization only if the parameter space is d=1 dimensional time. In d>1 quantization requires a fundamental length scale, and any bosonic field generates a spinorial wave function, leading to the purely quantum-theoretical emergence of spinors as a byproduct. We provide a probabilistic interpretation of the wave functions for the fields, and apply the formalism to a number of simple examples. These show that covariant canonical quantization produces both the Klein-Gordon and the Dirac equation, while also predicting the existence of discrete towers of identically charged fermions with different masses.
E. Laenen
2011-01-01
The theoretical aspects of a number of top quark properties such as its mass and its couplings are reviewed. Essential aspects in the theoretical description of top quark production, singly, in pairs and in association, as well as its decay related to spin and angular correlations are discussed.
Indian Academy of Sciences (India)
Eric Laenen
2012-10-01
The theoretical aspects of a number of top quark properties such as its mass and its couplings are reviewed. Essential aspects in the theoretical description of top quark production, singly, in pairs and in association, as well as its decay related to spin and angular correlations are discussed.
Covariance Applications with Kiwi
Mattoon, C. M.; Brown, D.; Elliott, J. B.
2012-05-01
The Computational Nuclear Physics group at Lawrence Livermore National Laboratory (LLNL) is developing a new tool, named `Kiwi', that is intended as an interface between the covariance data increasingly available in major nuclear reaction libraries (including ENDF and ENDL) and large-scale Uncertainty Quantification (UQ) studies. Kiwi is designed to integrate smoothly into large UQ studies, using the covariance matrix to generate multiple variations of nuclear data. The code has been tested using critical assemblies as a test case, and is being integrated into LLNL's quality assurance and benchmarking for nuclear data.
Covariance Applications with Kiwi
Directory of Open Access Journals (Sweden)
Elliott J.B.
2012-05-01
Full Text Available The Computational Nuclear Physics group at Lawrence Livermore National Laboratory (LLNL is developing a new tool, named ‘Kiwi’, that is intended as an interface between the covariance data increasingly available in major nuclear reaction libraries (including ENDF and ENDL and large-scale Uncertainty Quantification (UQ studies. Kiwi is designed to integrate smoothly into large UQ studies, using the covariance matrix to generate multiple variations of nuclear data. The code has been tested using critical assemblies as a test case, and is being integrated into LLNL's quality assurance and benchmarking for nuclear data.
Energy Technology Data Exchange (ETDEWEB)
Erbacher, Robin D.; /UC, Davis
2005-10-01
While the top quark was discovered in 1995 at the Fermilab Tevatron, a decade later they still have very little information about the top. As the heaviest particle yet discovered, the top quark is interesting in and of itself, but some speculate that it may play a special role in physics beyond the Standard Model. With Run 2 of the Tevatron well underway, they have the opportunity to study top quark properties with much better sensitivity, and to test whether top quarks behave as predicted by current theories. This article focuses on the basics of top quark physics at the Tevatron, highlighting only a sample of the many recent measurements, as new results are being released monthly, and constantly changing the landscape of our knowledge of top.
The quark-gluon vertex in Landau gauge bound-state studies
Williams, Richard
2014-01-01
We present a practical method for the solution of the quark-gluon vertex for use in Bethe--Salpeter and Dyson--Schwinger calculations. The efficient decomposition into the necessary covariants is detailed, with the numerical algorithm outlined for both real and complex Euclidean momenta. A model suitable for bound-state calculations is given together with results for the quark propagator and quark-gluon vertex for different quark flavours. The relative impact of the various components of the quark-gluon vertex is highlighted with the flavour dependence of the effective quark-gluon interaction obtained, thus providing insight for the construction of phenomenological models within Rainbow-Ladder. Finally, we solve the corresponding Green's functions for complex Euclidean momenta as required for practical calculations.
Light Quark Mass Effects in Bottom Quark Mass Determinations
Hoang, A. H.
2001-01-01
Recent results for charm quark mass effects in perturbative bottom quark mass determinations from $\\Upsilon$ mesons are reviewed. The connection between the behavior of light quark mass corrections and the infrared sensitivity of some bottom quark mass definitions is examined in some detail.
From hadron gas to quark matter, 1
Hagedorn, Rolf
1981-01-01
An analytical, non-perturbative description of a strongly interacting hadron gas is presented. Its main features are: the formulation is relativistically covariant, hadrons have finite extensions which are treated a la Van der Waals and their strong interactions are simulated by a hadronic mass spectrum generated by a bootstrap equation under the constraints of baryon number conservation. The system exhibits a singularity, which has the typical features of a phase transition gas to liquid, but which the authors interpret here as the transition into a quark-gluon plasma phase, which, however, cannot be described by this model. (16 refs).
Generalized Linear Covariance Analysis
Carpenter, James R.; Markley, F. Landis
2014-01-01
This talk presents a comprehensive approach to filter modeling for generalized covariance analysis of both batch least-squares and sequential estimators. We review and extend in two directions the results of prior work that allowed for partitioning of the state space into solve-for'' and consider'' parameters, accounted for differences between the formal values and the true values of the measurement noise, process noise, and textita priori solve-for and consider covariances, and explicitly partitioned the errors into subspaces containing only the influence of the measurement noise, process noise, and solve-for and consider covariances. In this work, we explicitly add sensitivity analysis to this prior work, and relax an implicit assumption that the batch estimator's epoch time occurs prior to the definitive span. We also apply the method to an integrated orbit and attitude problem, in which gyro and accelerometer errors, though not estimated, influence the orbit determination performance. We illustrate our results using two graphical presentations, which we call the variance sandpile'' and the sensitivity mosaic,'' and we compare the linear covariance results to confidence intervals associated with ensemble statistics from a Monte Carlo analysis.
Masses and magnetic moments of ground-state baryons in covariant baryon chiral perturbation theory
Geng, L S; Alvarez-Ruso, L; Vicente-Vacas, M J
2012-01-01
We report on some recent developments in our understanding of the light-quark mass dependence and the SU(3) flavor symmetry breaking corrections to the magnetic moments of the ground-state baryons in a covariant formulation of baryon chiral perturbation theory, the so-called EOMS formulation. We show that this covariant ChPT exhibits some promising features compared to its heavy-baryon and infrared counterparts.
Baryon Spectrum Analysis using Covariant Constraint Dynamics
Whitney, Joshua; Crater, Horace
2012-03-01
The energy spectrum of the baryons is determined by treating each of them as a three-body system with the interacting forces coming from a set of two-body potentials that depend on both the distance between the quarks and the spin and orbital angular momentum coupling terms. The Two Body Dirac equations of constraint dynamics derived by Crater and Van Alstine, matched with the quasipotential formalism of Todorov as the underlying two-body formalism are used, as well as the three-body constraint formalism of Sazdjian to integrate the three two-body equations into a single relativistically covariant three body equation for the bound state energies. The results are analyzed and compared to experiment using a best fit method and several different algorithms, including a gradient approach, and Monte Carlo method. Results for all well-known baryons are presented and compared to experiment, with good accuracy.
Deeply virtual Compton scattering in a relativistic quark model
Energy Technology Data Exchange (ETDEWEB)
Spitzenberg, T.
2007-09-15
This thesis is mainly concerned with a model calculation for generalized parton distributions (GPDs). We calculate vectorial- and axial GPDs for the N{yields}N and N{yields}{delta} transition in the framework of a light front quark model. This requires the elaboration of a connection between transition amplitudes and GPDs. We provide the first quark model calculations for N{yields}{delta} GPDs. The examination of transition amplitudes leads to various model independent consistency relations. These relations are not exactly obeyed by our model calculation since the use of the impulse approximation in the light front quark model leads to a violation of Poincare covariance. We explore the impact of this covariance breaking on the GPDs and form factors which we determine in our model calculation and find large effects. The reference frame dependence of our results which originates from the breaking of Poincare covariance can be eliminated by introducing spurious covariants. We extend this formalism in order to obtain frame independent results from our transition amplitudes. (orig.)
Fritzsch, Harald
1983-01-01
Quark rossi, verdi e blu ; quark dotati di stranezza e di incanto ; quark 'su' e 'giù' : sembra che i fisici delle particelle giochino a confondere la curiosità del profano, con queste denominazioni fantasiose. Che cosa significano ? e, soprattutto, i quark sono i costituenti davvero elementari della materia ?
Huang, Z; Huang, Zheng
1993-01-01
We study the behavior of the self-mass for a quark with a current mass larger than $\\Lambda_QCD$, as a function of its Euclidean momentum and mass, in QCD. An expression for the Bethe-Salpeter kernel of the Schwinger-Dyson (SD) equation valid in both the infrared and ultraviolet regions is obtained based on a renormalization group analysis. The resulting SD equation is solved numerically. It is found that the quark constituent mass at zero momentum is substantially enhanced due to its effective gauge interaction. The solution in the ultraviolet region agrees well with the known asymptotic solution. The self-mass scales exactly as the on-shell current mass at a fixed momentum.
Top quark measurements at ATLAS
Grancagnolo, Sergio; The ATLAS collaboration
2017-01-01
The top quark is the heaviest known fundamental particle. As it is the only quark that decays before it hadronizes, this gives us the unique opportunity to probe the properties of bare quarks at the Large Hadron Collider. This talk will present highlights of a few recent precision measurements by the ATLAS Collaboration of the top quark using 13 TeV and 8 TeV collision data: top-quark pair and single top production cross sections including differential distributions will be presented alongside top quark properties measurements. These measurements, including results using boosted top quarks, probe our understanding of top quark production in the TeV regime. Measurements of the top quark mass and searches for rare top quark decays are also presented.
Leitão, Sofia; Stadler, Alfred; Peña, M. T.; Biernat, Elmar P.
2017-01-01
The Covariant Spectator Theory (CST) is used to calculate the mass spectrum and vertex functions of heavy-light and heavy mesons in Minkowski space. The covariant kernel contains Lorentz scalar, pseudoscalar, and vector contributions. The numerical calculations are performed in momentum space, where special care is taken to treat the strong singularities present in the confining kernel. The observed meson spectrum is very well reproduced after fitting a small number of model parameters. Remarkably, a fit to a few pseudoscalar meson states only, which are insensitive to spin-orbit and tensor forces and do not allow to separate the spin-spin from the central interaction, leads to essentially the same model parameters as a more general fit. This demonstrates that the covariance of the chosen interaction kernel is responsible for the very accurate prediction of the spin-dependent quark-antiquark interactions.
Leitão, Sofia; Peña, M T; Biernat, Elmar P
2016-01-01
The Covariant Spectator Theory (CST) is used to calculate the mass spectrum and vertex functions of heavy-light and heavy mesons in Minkowski space. The covariant kernel contains Lorentz scalar, pseudoscalar, and vector contributions. The numerical calculations are performed in momentum space, where special care is taken to treat the strong singularities present in the confining kernel. The observed meson spectrum is very well reproduced after fitting a small number of model parameters. Remarkably, a fit to a few pseudoscalar meson states only, which are insensitive to spin-orbit and tensor forces and do not allow to separate the spin-spin from the central interaction, leads to essentially the same model parameters as a more general fit. This demonstrates that the covariance of the chosen interaction kernel is responsible for the very accurate prediction of the spin-dependent quark-antiquark interactions.
Institute of Scientific and Technical Information of China (English)
ZONG Hong-Shi; PING Jia-Lun; SUN Wei-Min; CHANG Chao-Hsi; WANG Fan
2002-01-01
We exhibit a method for obtaining the low chemical potential dependence of the dressed quark propagatorfrom an effective quark-quark interaction model. Within this approach we explore the chemical potential dependenceof the dressed-quark propagator, which provides a means of determining the behavior of the chiral and deconfinementorder parameters. A comparison with the results of previous researches is given.
Saltas, Ippocratis D
2016-01-01
We derive the 1-loop effective action of the cubic Galileon coupled to quantum-gravitational fluctuations in a background and gauge-independent manner, employing the covariant framework of DeWitt and Vilkovisky. Although the bare action respects shift symmetry, the coupling to gravity induces an effective mass to the scalar, of the order of the cosmological constant, as a direct result of the non-flat field-space metric, the latter ensuring the field-reparametrization invariance of the formalism. Within a gauge-invariant regularization scheme, we discover novel, gravitationally induced non-Galileon higher-derivative interactions in the effective action. These terms, previously unnoticed within standard, non-covariant frameworks, are not Planck suppressed. Unless tuned to be sub-dominant, their presence could have important implications for the classical and quantum phenomenology of the theory.
Covariant approximation averaging
Shintani, Eigo; Blum, Thomas; Izubuchi, Taku; Jung, Chulwoo; Lehner, Christoph
2014-01-01
We present a new class of statistical error reduction techniques for Monte-Carlo simulations. Using covariant symmetries, we show that correlation functions can be constructed from inexpensive approximations without introducing any systematic bias in the final result. We introduce a new class of covariant approximation averaging techniques, known as all-mode averaging (AMA), in which the approximation takes account of contributions of all eigenmodes through the inverse of the Dirac operator computed from the conjugate gradient method with a relaxed stopping condition. In this paper we compare the performance and computational cost of our new method with traditional methods using correlation functions and masses of the pion, nucleon, and vector meson in $N_f=2+1$ lattice QCD using domain-wall fermions. This comparison indicates that AMA significantly reduces statistical errors in Monte-Carlo calculations over conventional methods for the same cost.
Using Analysis of Covariance (ANCOVA) with Fallible Covariates
Culpepper, Steven Andrew; Aguinis, Herman
2011-01-01
Analysis of covariance (ANCOVA) is used widely in psychological research implementing nonexperimental designs. However, when covariates are fallible (i.e., measured with error), which is the norm, researchers must choose from among 3 inadequate courses of action: (a) know that the assumption that covariates are perfectly reliable is violated but…
Using Analysis of Covariance (ANCOVA) with Fallible Covariates
Culpepper, Steven Andrew; Aguinis, Herman
2011-01-01
Analysis of covariance (ANCOVA) is used widely in psychological research implementing nonexperimental designs. However, when covariates are fallible (i.e., measured with error), which is the norm, researchers must choose from among 3 inadequate courses of action: (a) know that the assumption that covariates are perfectly reliable is violated but…
Energy Technology Data Exchange (ETDEWEB)
Parke, S.
1998-01-01
In this presentation I will primarily focus on top quark physics but I will include a discussion of the W-boson mass and the possibility of discovering a light Higgs boson via associated production at the Tevatron.
Guichon, P A M; Thomas, A W
1996-01-01
We describe the development of a theoretical description of the structure of finite nuclei based on a relativistic quark model of the structure of the bound nucleons which interact through the (self-consistent) exchange of scalar and vector mesons.
Indian Academy of Sciences (India)
Narendra Singh
2003-01-01
Assuming a relation between the quark mass matrices of the two sectors a unique solution can be obtained for the CKM ﬂavor mixing matrix. A numerical example is worked out which is in excellent agreement with experimental data.
DEFF Research Database (Denmark)
Sørensen, Paul Haase; Taylor, John C.
1984-01-01
Processes with coloured particles in the initial state are generally infrared divergent. We investigate the effect of this on processes with colourless particles in the initial state, when the amplitude is near an intermediate quark pole. The result is a characteristic logarithmic depedence...... on the 'binding energy'(even though spectator interactions are taken into account), and the result is gauge-invariant. Summed to all orders the logarithms could perhaps suppress the quark pole....
Hadronic correction to Coulomb potential between quarks and diquark structure
Energy Technology Data Exchange (ETDEWEB)
Xin-Heng, Guo [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); Xue-Qian, Li; Peng-Nian, Shen [Academia Sinica, Beijing, BJ (China). Inst. of High Energy Physics; Chuang, Wang [Nankai Univ., TJ (China). Dept. of Physics
1997-07-01
We have studied the hadronic correction from the background pion fields due to the chiral symmetry breaking to the Coulomb potential that governs the short-distance behavior of the interactions between the bound quarks. The background fields are associated with the constituent quark mass. We find a modified form which favors the diquark structure. We also roughly estimate an influence of this correction on the phase shifts in nucleon scattering and find that it may cause an extra middle range attraction between nucleons which is expected. (author) 17 refs., 4 figs.
Covariant Magnetic Connection Hypersurfaces
Pegoraro, F
2016-01-01
In the single fluid, nonrelativistic, ideal-Magnetohydrodynamic (MHD) plasma description magnetic field lines play a fundamental role by defining dynamically preserved "magnetic connections" between plasma elements. Here we show how the concept of magnetic connection needs to be generalized in the case of a relativistic MHD description where we require covariance under arbitrary Lorentz transformations. This is performed by defining 2-D {\\it magnetic connection hypersurfaces} in the 4-D Minkowski space. This generalization accounts for the loss of simultaneity between spatially separated events in different frames and is expected to provide a powerful insight into the 4-D geometry of electromagnetic fields when ${\\bf E} \\cdot {\\bf B} = 0$.
Universality of Covariance Matrices
Pillai, Natesh S
2011-01-01
We prove the universality of covariance matrices of the form $H_{N \\times N} = {1 \\over N} \\tp{X}X$ where $[X]_{M \\times N}$ is a rectangular matrix with independent real valued entries $[x_{ij}]$ satisfying $\\E \\,x_{ij} = 0$ and $\\E \\,x^2_{ij} = {1 \\over M}$, $N, M\\to \\infty$. Furthermore it is assumed that these entries have sub-exponential tails. We will study the asymptotics in the regime $N/M = d_N \\in (0,\\infty), \\lim_{N\\to \\infty}d_N \
Covariant Projective Extensions
Institute of Scientific and Technical Information of China (English)
许天周; 梁洁
2003-01-01
@@ The theory of crossed products of C*-algebras by groups of automorphisms is a well-developed area of the theory of operator algebras. Given the importance and the success ofthat theory, it is natural to attempt to extend it to a more general situation by, for example,developing a theory of crossed products of C*-algebras by semigroups of automorphisms, or evenof endomorphisms. Indeed, in recent years a number of papers have appeared that are concernedwith such non-classicaltheories of covariance algebras, see, for instance [1-3].
Octet to decuplet electromagnetic transition in a relativistic quark model
Ramalho, G
2013-01-01
We study the octet to decuplet baryon electromagnetic transitions using the covariant spectator quark model, and predict the transition magnetic dipole form factors for those involving the strange baryons. Utilizing SU(3) symmetry, the valence quark contributions are supplemented by the pion cloud dressing based on the one estimated in the $\\gamma^\\ast N \\to \\Delta$ reaction. Although the valence quark contributions are dominant in general, the pion cloud effects turn out to be very important to describe the experimental data. We also show that, other mesons besides the pion in particular the kaon, may be relevant for some reactions such as $\\gamma^\\ast \\Sigma^+ \\to \\Sigma^{*+}$, based on our analysis for the radiative decay widths of the strange decuplet baryons.
Earth Observing System Covariance Realism
Zaidi, Waqar H.; Hejduk, Matthew D.
2016-01-01
The purpose of covariance realism is to properly size a primary object's covariance in order to add validity to the calculation of the probability of collision. The covariance realism technique in this paper consists of three parts: collection/calculation of definitive state estimates through orbit determination, calculation of covariance realism test statistics at each covariance propagation point, and proper assessment of those test statistics. An empirical cumulative distribution function (ECDF) Goodness-of-Fit (GOF) method is employed to determine if a covariance is properly sized by comparing the empirical distribution of Mahalanobis distance calculations to the hypothesized parent 3-DoF chi-squared distribution. To realistically size a covariance for collision probability calculations, this study uses a state noise compensation algorithm that adds process noise to the definitive epoch covariance to account for uncertainty in the force model. Process noise is added until the GOF tests pass a group significance level threshold. The results of this study indicate that when outliers attributed to persistently high or extreme levels of solar activity are removed, the aforementioned covariance realism compensation method produces a tuned covariance with up to 80 to 90% of the covariance propagation timespan passing (against a 60% minimum passing threshold) the GOF tests-a quite satisfactory and useful result.
Lattice renormalization of the static quark derivative operator
Blossier, B; Morénas, V; Pène, O
2006-01-01
We give the analytical expressions and numerical values of radiative corrections to the covariant derivative operator on the static quark line, used for the lattice calculation of the Isgur-Wise form factors $\\tau_{1/2}(1)$ and $\\tau_{3/2}(1)$. Those corrections induce an enhancement of renormalized quantities if an hypercubic blocking is applied to the Wilson line, whereas there is a reduction without such a blocking.
Proton transversity and intrinsic motion of the quarks
Závada, P
2005-01-01
The spin structure of the system of quasifree fermions having total angular momentum $J=1/2$ is studied in a consistently covariant approach. Within this model the relations between the spin functions are obtained. Their particular cases are the sum rules Wanzura - Wilczek, Efremov - Leader - Teryaev, Burkhardt - Cottingham and also the expression for the Wanzura - Wilczek twist 2 term $g_{2}^{WW}$. With the use of the proton valence quark distributions as an input, the corresponding spin functions including transversity are obtained.
Land, M C
2001-01-01
This paper examines the Stark effect, as a first order perturbation of manifestly covariant hydrogen-like bound states. These bound states are solutions to a relativistic Schr\\"odinger equation with invariant evolution parameter, and represent mass eigenstates whose eigenvalues correspond to the well-known energy spectrum of the non-relativistic theory. In analogy to the nonrelativistic case, the off-diagonal perturbation leads to a lifting of the degeneracy in the mass spectrum. In the covariant case, not only do the spectral lines split, but they acquire an imaginary part which is lnear in the applied electric field, thus revealing induced bound state decay in first order perturbation theory. This imaginary part results from the coupling of the external field to the non-compact boost generator. In order to recover the conventional first order Stark splitting, we must include a scalar potential term. This term may be understood as a fifth gauge potential, which compensates for dependence of gauge transformat...
Recursive fragmentation model with quark spin. Application to quark polarimetry
Artru, X
2010-01-01
An elementary recursive model accounting for the quark spin in the fragmentation of a quark into mesons is presented. The quark spin degree of freedom is represented by a two-components spinor. Spin one meson can be included. The model produces Collins effect and jet handedness. The influence of the initial quark polarisation decays exponentially with the rank of the meson, at dierent rates for longitudinal and transverse polarisations
Bootstrapping quarks and gluons
Energy Technology Data Exchange (ETDEWEB)
Chew, G.F.
1979-04-01
Dual topological unitarization (DTU) - the approach to S-matrix causality and unitarity through combinatorial topology - is reviewed. Amplitudes associated with triangulated spheres are shown to constitute the core of particle physics. Each sphere is covered by triangulated disc faces corresponding to hadrons. The leading current candidate for the hadron-face triangulation pattern employs 3-triangle basic subdiscs whose orientations correspond to baryon number and topological color. Additional peripheral triangles lie along the hadron-face perimeter. Certain combinations of peripheral triangles with a basic-disc triangle can be identified as quarks, the flavor of a quark corresponding to the orientation of its edges that lie on the hadron-face perimeter. Both baryon number and flavor are additively conserved. Quark helicity, which can be associated with triangle-interior orientation, is not uniformly conserved and interacts with particle momentum, whereas flavor does not. Three different colors attach to the 3 quarks associated with a single basic subdisc, but there is no additive physical conservation law associated with color. There is interplay between color and quark helicity. In hadron faces with more than one basic subdisc, there may occur pairs of adjacent flavorless but colored triangles with net helicity +-1 that are identifiable as gluons. Broken symmetry is an automatic feature of the bootstrap. T, C and P symmetries, as well as up-down flavor symmetry, persist on all orientable surfaces.
Rizzo, T G
1979-01-01
The weak decay of heavy b and t quarks is discussed using the mixing angles obtained in Fritzsch's model (1978). The author finds that the decay b to c dominates over b to u for 7
A covariant model for the nucleon spin structure
Ramalho, G
2015-01-01
We present the results of the covariant spectator quark model applied to the nucleon structure function $f(x)$ measured in unpolarized deep inelastic scattering, and the structure functions $g_1(x)$ and $g_2(x)$ measured in deep inelastic scattering using polarized beams and targets ($x$ is the Bjorken scaling variable). The nucleon is modeled by a valence quark-diquark structure with $S,P$ and $D$ components. The shape of the wave functions and the relative strength of each component are fixed by making fits to the deep inelastic scattering data for the structure functions $f(x)$ and $g_1(x)$. The model is then used to make predictions on the function $g_2(x)$ for the proton and neutron.
The Quark's Model and Confinement
Novozhilov, Yuri V.
1977-01-01
Quarks are elementary particles considered to be components of the proton, the neutron, and others. This article presents the quark model as a mathematical concept. Also discussed are gluons and bag models. A bibliography is included. (MA)
The Quark's Model and Confinement
Novozhilov, Yuri V.
1977-01-01
Quarks are elementary particles considered to be components of the proton, the neutron, and others. This article presents the quark model as a mathematical concept. Also discussed are gluons and bag models. A bibliography is included. (MA)
Mulders, Martijn
2016-01-01
Ever since the discovery of the top quark at the Tevatron collider in 1995 the measurement of its mass has been a high priority. As one of the fundamental parameters of the Standard Theory of particle physics, the precise value of the top quark mass together with other inputs provides a test for the self-consistency of the theory, and has consequences for the stability of the Higgs field that permeates the Universe. In this review I will briefly summarize the experimental techniques used at the Tevatron and the LHC experiments throughout the years to measure the top quark mass with ever improving accuracy, and highlight the recent progress in combining all measurements in a single world average combination. As experimental measurements became more precise, the question of their theoretical interpretation has become important. The difficulty of relating the measured quantity to the fundamental top mass parameter has inspired alternative measurement methods that extract the top mass in complementary ways. I wil...
Indian Academy of Sciences (India)
H Weigel
2003-11-01
In this talk I review studies of hadron properties in bosonized chiral quark models for the quark ﬂavor dynamics. Mesons are constructed from Bethe–Salpeter equations and baryons emerge as chiral solitons. Such models require regularization and I show that the two-fold Pauli–Villars regularization scheme not only fully regularizes the effective action but also leads the scaling laws for structure functions. For the nucleon structure functions the present approach serves to determine the regularization prescription for structure functions whose leading moments are not given by matrix elements of local operators. Some numerical results are presented for the spin structure functions.
Quark Orbital Angular Momentum
Directory of Open Access Journals (Sweden)
Burkardt Matthias
2015-01-01
Full Text Available Definitions of orbital angular momentum based on Wigner distributions are used as a framework to discuss the connection between the Ji definition of the quark orbital angular momentum and that of Jaffe and Manohar. We find that the difference between these two definitions can be interpreted as the change in the quark orbital angular momentum as it leaves the target in a DIS experiment. The mechanism responsible for that change is similar to the mechanism that causes transverse single-spin asymmetries in semi-inclusive deep-inelastic scattering.
Hubeny, Veronika E
2014-01-01
A recently explored interesting quantity in AdS/CFT, dubbed 'residual entropy', characterizes the amount of collective ignorance associated with either boundary observers restricted to finite time duration, or bulk observers who lack access to a certain spacetime region. However, the previously-proposed expression for this quantity involving variation of boundary entanglement entropy (subsequently renamed to 'differential entropy') works only in a severely restrictive context. We explain the key limitations, arguing that in general, differential entropy does not correspond to residual entropy. Given that the concept of residual entropy as collective ignorance transcends these limitations, we identify two correspondingly robust, covariantly-defined constructs: a 'strip wedge' associated with boundary observers and a 'rim wedge' associated with bulk observers. These causal sets are well-defined in arbitrary time-dependent asymptotically AdS spacetimes in any number of dimensions. We discuss their relation, spec...
Deriving covariant holographic entanglement
Dong, Xi; Lewkowycz, Aitor; Rangamani, Mukund
2016-11-01
We provide a gravitational argument in favour of the covariant holographic entanglement entropy proposal. In general time-dependent states, the proposal asserts that the entanglement entropy of a region in the boundary field theory is given by a quarter of the area of a bulk extremal surface in Planck units. The main element of our discussion is an implementation of an appropriate Schwinger-Keldysh contour to obtain the reduced density matrix (and its powers) of a given region, as is relevant for the replica construction. We map this contour into the bulk gravitational theory, and argue that the saddle point solutions of these replica geometries lead to a consistent prescription for computing the field theory Rényi entropies. In the limiting case where the replica index is taken to unity, a local analysis suffices to show that these saddles lead to the extremal surfaces of interest. We also comment on various properties of holographic entanglement that follow from this construction.
Deriving covariant holographic entanglement
Dong, Xi; Rangamani, Mukund
2016-01-01
We provide a gravitational argument in favour of the covariant holographic entanglement entropy proposal. In general time-dependent states, the proposal asserts that the entanglement entropy of a region in the boundary field theory is given by a quarter of the area of a bulk extremal surface in Planck units. The main element of our discussion is an implementation of an appropriate Schwinger-Keldysh contour to obtain the reduced density matrix (and its powers) of a given region, as is relevant for the replica construction. We map this contour into the bulk gravitational theory, and argue that the saddle point solutions of these replica geometries lead to a consistent prescription for computing the field theory Renyi entropies. In the limiting case where the replica index is taken to unity, a local analysis suffices to show that these saddles lead to the extremal surfaces of interest. We also comment on various properties of holographic entanglement that follow from this construction.
Covariant Macroscopic Quantum Geometry
Hogan, Craig J
2012-01-01
A covariant noncommutative algebra of position operators is presented, and interpreted as the macroscopic limit of a geometry that describes a collective quantum behavior of the positions of massive bodies in a flat emergent space-time. The commutator defines a quantum-geometrical relationship between world lines that depends on their separation and relative velocity, but on no other property of the bodies, and leads to a transverse uncertainty of the geometrical wave function that increases with separation. The number of geometrical degrees of freedom in a space-time volume scales holographically, as the surface area in Planck units. Ongoing branching of the wave function causes fluctuations in transverse position, shared coherently among bodies with similar trajectories. The theory can be tested using appropriately configured Michelson interferometers.
Saltas, Ippocratis D.; Vitagliano, Vincenzo
2017-05-01
We derive the 1-loop effective action of the cubic Galileon coupled to quantum-gravitational fluctuations in a background and gauge-independent manner, employing the covariant framework of DeWitt and Vilkovisky. Although the bare action respects shift symmetry, the coupling to gravity induces an effective mass to the scalar, of the order of the cosmological constant, as a direct result of the nonflat field-space metric, the latter ensuring the field-reparametrization invariance of the formalism. Within a gauge-invariant regularization scheme, we discover novel, gravitationally induced non-Galileon higher-derivative interactions in the effective action. These terms, previously unnoticed within standard, noncovariant frameworks, are not Planck suppressed. Unless tuned to be subdominant, their presence could have important implications for the classical and quantum phenomenology of the theory.
Covariant holographic entanglement negativity
Chaturvedi, Pankaj; Sengupta, Gautam
2016-01-01
We conjecture a holographic prescription for the covariant entanglement negativity of $d$-dimensional conformal field theories dual to non static bulk $AdS_{d+1}$ gravitational configurations in the framework of the $AdS/CFT$ correspondence. Application of our conjecture to a $AdS_3/CFT_2$ scenario involving bulk rotating BTZ black holes exactly reproduces the entanglement negativity of the corresponding $(1+1)$ dimensional conformal field theories and precisely captures the distillable quantum entanglement. Interestingly our conjecture for the scenario involving dual bulk extremal rotating BTZ black holes also accurately leads to the entanglement negativity for the chiral half of the corresponding $(1+1)$ dimensional conformal field theory at zero temperature.
Quark Helicity and Transversity Distributions
Hwang, Dae Sung
2016-01-01
The quark transversity distribution inside nucleon is less understood than the quark unpolarized and helicity distributions inside nucleon. In particular, it is important to know clearly why the quark helicity and transversity distributions are different. We investigate the origin of their discrepancy.
Color confinement multi quark resonance
Energy Technology Data Exchange (ETDEWEB)
Wang Fan [Department of Physics, Nanjing University, Joint Center for Particle Nuclear Physics and Cosmology, Nanjing University and Pupil Mountain Observatory, Nanjing, 210008 (China); Ping, J.L. [Department of Physics, Nanjing Normal University, Nanjing, 210097 (China); Pang, H.R. [Department of Physics, Southeast University, Nanjing, 210008 (China); Chen, L.Z. [Department of Physics, Nanjing University, Joint Center for Particle Nuclear Physics and Cosmology, Nanjing University and Pupil Mountain Observatory, Nanjing, 210008 (China)
2007-06-15
A new kind microscopic resonance, the color confinement multi quark resonance is proposed and studied. The quark delocalization color screening model is compared to one of the chiral quark model, the Salamanca model, and a new mechanism of the intermediate range NN interaction, the mutual distortion of interacting nucleons, is checked to be similar to the {sigma} meson exchange.
Energy Technology Data Exchange (ETDEWEB)
Pang, Yang [Columbia Univ., New York, NY (United States)]|[Brookhaven National Labs., Upton, NY (United States)
1997-09-22
Many phenomenological models for relativistic heavy ion collisions share a common framework - the relativistic Boltzmann equations. Within this framework, a nucleus-nucleus collision is described by the evolution of phase-space distributions of several species of particles. The equations can be effectively solved with the cascade algorithm by sampling each phase-space distribution with points, i.e. {delta}-functions, and by treating the interaction terms as collisions of these points. In between collisions, each point travels on a straight line trajectory. In most implementations of the cascade algorithm, each physical particle, e.g. a hadron or a quark, is often represented by one point. Thus, the cross-section for a collision of two points is just the cross-section of the physical particles, which can be quite large compared to the local density of the system. For an ultra-relativistic nucleus-nucleus collision, this could lead to a large violation of the Lorentz invariance. By using the invariance property of the Boltzmann equation under a scale transformation, a Lorentz invariant cascade algorithm can be obtained. The General Cascade Program - GCP - is a tool for solving the relativistic Boltzmann equation with any number of particle species and very general interactions with the cascade algorithm.
Bayes linear covariance matrix adjustment
Wilkinson, Darren J
1995-01-01
In this thesis, a Bayes linear methodology for the adjustment of covariance matrices is presented and discussed. A geometric framework for quantifying uncertainties about covariance matrices is set up, and an inner-product for spaces of random matrices is motivated and constructed. The inner-product on this space captures aspects of our beliefs about the relationship between covariance matrices of interest to us, providing a structure rich enough for us to adjust beliefs about unknown matrices in the light of data such as sample covariance matrices, exploiting second-order exchangeability and related specifications to obtain representations allowing analysis. Adjustment is associated with orthogonal projection, and illustrated with examples of adjustments for some common problems. The problem of adjusting the covariance matrices underlying exchangeable random vectors is tackled and discussed. Learning about the covariance matrices associated with multivariate time series dynamic linear models is shown to be a...
Comment on a confining theory of quarks, leptons and sarks
Yasuè, Masaki
1990-12-01
The confining SU(2) Lloc theory for composite quarks, leptons and extra weak-triplet and -singlet fermions (called sarks), which fixes the generation number ⩽3 as suggested by Frampton and Ng in their sark model, is shown to incorporate extra composite W and Z bosons, W‧ and Z‧, as the remnant of confined hypercolors carried by sark constituents. The model deals with SU(2) Lloc -and hypercolor-singlet composites that exhibit the duality of compositeness and “elementariness”, in which it differs from the original sark model of Frampton and Ng. W‧ and Z‧ primarily couple to sarks but not to quarks and leptons while the indirect coupling of Z‧ to quarks and leptons is induced as a result of the vector meson dominance of the photon.
Quark-antiquark bound-state spectroscopy and QCD
Energy Technology Data Exchange (ETDEWEB)
Bloom, E.D.
1982-11-01
The discussion covers quarks as we know them, the classification of ordinary mesons in terms of constituent quarks, hidden charm states and charmed mesons, bottom quarks, positronium as a model for quarti q, quantum chromodynamics and its foundation in experiment, the charmonium model, the mass of states, fine structure and hyperfine structure, classification, widths of states, rate and multipolarity of gamma transitions, questions about bottom, leptonic widths and the determination of Q/sub b/, the mass splitting of the n/sup 3/S/sub 1/ states, the center of gravity of the masses of the n/sup 3/P; states, n/sup 3/ P; fine structure and classification, branching ratios for upsilon' ..-->.. tau chi/sub 6j/ and the tau cascade reactions, hyperfine splitting, and top. (GHT)
De Sanctis, M; Santopinto, E; Vassallo, A
2015-01-01
We briefly describe our relativistic quark-diquark model, developed within the framework of point form dynamics, which is the relativistic extension of the interacting quark-diquark model. In order to do that we have to show the main properties and quantum numbers of the effective degree of freedom of constituent diquark. Our results for the nonstrange baryon spectrum and for the nucleon electromagnetic form factors are discussed.
Gluon chains and the quark-antiquark potential
Greensite, J
2009-01-01
The flux tube between a quark and an antiquark in Coulomb gauge is imagined in the gluon-chain model as a sequence of constituent gluons bound together by Coulombic nearest-neighbor interactions. We diagonalize the transfer matrix in SU(2) lattice gauge theory in a finite basis of states containing a static quark-antiquark pair together with zero, one, and two gluons in Coulomb gauge. We show that while the string tension of the color-Coulomb potential (obtained from the zero-gluon to zero-gluon element of the transfer matrix) overshoots the true asymptotic string tension by a factor of about three, the inclusion of a few states with constituent gluons reduces the discrepancy considerably. The minimal energy eigenstate of the transfer matrix in the zero-, one-, and two-gluon basis exhibits a linearly rising potential with the string tension only about 1.4 times larger than the asymptotic one.
Covariant Thermodynamics and Relativity
Lopez-Monsalvo, C S
2011-01-01
This thesis deals with the dynamics of irreversible processes within the context of the general theory of relativity. In particular, we address the problem of the 'infinite' speed of propagation of thermal disturbances in a dissipative fluid. The present work builds on the multi-fluid variational approach to relativistic dissipation, pioneered by Carter, and provides a dynamical theory of heat conduction. The novel property of such approach is the thermodynamic interpretation associated with a two-fluid system whose constituents are matter and entropy. The dynamics of this model leads to a relativistic generalisation of the Cattaneo equation; the constitutive relation for causal heat transport. A comparison with the Israel and Stewart model is presented and its equivalence is shown. This discussion provides new insights into the not-well understood definition of a non-equilibrium temperature. The variational approach to heat conduction presented in this thesis constitutes a mathematically promising formalism ...
Demilly, A; The ATLAS collaboration
2014-01-01
Properties of the top quark are measured with the ATLAS detector using LHC proton-proton collisions data. Measurements of the top-quark mass and polarisation, as well as of the polarization of W bosons in top quark decays to probe the Wtb-vertex are presented. In addition, measurements of the spin correlation between top and anti-top quarks as well as of the top- quark charge asymmetry, which constitute important tests of QCD and are sensitive to new physics, are discussed.
Transverse-momentum dependent parton distribution functions beyond leading twist in quark models
Lorcé, C; Schweitzer, P
2014-01-01
Higher-twist transverse momentum dependent parton distribution functions (TMDs) are a valuable probe of the quark-gluon dynamics in the nucleon, and play a vital role for the explanation of sizable azimuthal asymmetries in hadron production from unpolarized and polarized deep-inelastic lepton-nucleon scattering observed in experiments at CERN, DESY and Jefferson Lab. The associated observables are challenging to interpret, and still await a complete theoretical explanation, which makes guidance from models valuable. In this work we establish the formalism to describe unpolarized higher-twist TMDs in the light-front framework based on a Fock-space expansion of the nucleon state in terms of free on-shell parton states. We derive general expressions and present numerical results in a practical realization of this picture provided by the light-front constituent quark model. We review several other popular quark model approaches including free quark ensemble, bag, spectator and chiral quark-soliton model.
Energy Technology Data Exchange (ETDEWEB)
Maki, Tuula [Univ. of Helsinki (Finland)
2008-03-18
The top quark is the heaviest elementary particle. Its mass is one of the fundamental parameters of the standard model of particle physics, and an important input to precision electroweak tests. This thesis describes three measurements of the top-quark mass in the dilepton decay channel. The dilepton events have two neutrinos in the final state; neutrinos are weakly interacting particles that cannot be detected with a multipurpose experiment. Therefore, the signal of dilepton events consists of a large amount of missing energy and momentum carried off by the neutrinos. The top-quark mass is reconstructed for each event by assuming an additional constraint from a top mass independent distribution. Template distributions are constructed from simulated samples of signal and background events, and parametrized to form continuous probability density functions. The final top-quark mass is derived using a likelihood fit to compare the reconstructed top mass distribution from data to the parametrized templates. One of the analyses uses a novel technique to add top mass information from the observed number of events by including a cross-section-constraint in the likelihood function. All measurements use data samples collected by the CDF II detector.
Mulders, Martijn
2016-10-01
Ever since the discovery of the top quark at the Tevatron collider in 1995 the measurement of its mass has been a high priority. As one of the fundamental parameters of the Standard Theory of particle physics, the precise value of the top quark mass together with other inputs provides a test for the self-consistency of the theory, and has consequences for the stability of the Higgs field that permeates the Universe. In this review I will briefly summarize the experimental techniques used at the Tevatron and the LHC experiments throughout the years to measure the top quark mass with ever improving accuracy, and highlight the recent progress in combining all measurements in a single world average combination. As experimental measurements became more precise, the question of their theoretical interpretation has become important. The difficulty of relating the measured quantity to the fundamental top mass parameter has inspired alternative measurement methods that extract the top mass in complementary ways. I will discuss the status of those techniques and their results, and present a brief outlook of further improvements in the experimental determination of the top quark mass to be expected at the LHC and beyond.
Indian Academy of Sciences (India)
C P Singh
2000-04-01
Recent trends in the research of quark gluon plasma (QGP) are surveyed and the current experimental and theoretical status regarding the properties and signals of QGP is reported. We hope that the experiments commencing at relativistic heavy-ion collider (RHIC) in 2000 will provide a glimpse of the QGP formation.
Pallante, E.; Petronzio, R.
1995-01-01
We construct an effective Lagrangian for low energy hadronic interactions through an infinite expansion in inverse powers of the low energy cutoff Î›Ï‡ of all possible chiral invariant non-renormalizable interactions between quarks and mesons degrees of freedom arising from the bosonization of a gen
Quark nuggets search using gravitational waves aluminum bar detectors
Directory of Open Access Journals (Sweden)
Ronga Francesco
2016-01-01
Full Text Available Up to now there is no evidence of supersymmetric WIMPS dark matter. This may suggests to look for more exotic possibilities, for example compact ultra-dense quark nuggets. Nuclearites are an example of compact objects that could be constituent of the dark matter. After a short discussion on nuclearites, the result of a nuclearite search with the gravitational wave bar detectors NAUTILUS and EXPLORER is reported.
Study of Ratio of Proton Momentum Distributions with a Chiral Quark Model
Institute of Scientific and Technical Information of China (English)
LIU Jian; DONG Yu-Bing
2005-01-01
The ratio between the anomalous magnetic moments of proton and neutron has recently been suggested to be connected to the ratio of proton momentum fractions carried by the valence quarks inside it. This moment fraction ratio is respectively evaluated by using constituent quark model and chiral quark model in order to check meson cloud effect. Our results show that the meson cloud effect is remarkable to the ratio of the proton momentum fractions, and therefore, this ratiois a sensitive test for the meson cloud effect as well as for the SU(6) symmetry breaking effect.
The neutron electric dipole form factor in the perturbative chiral quark model
Dib, C; Gutsche, T; Kovalenko, S; Kuckei, J; Lyubovitskij, V E; Pumsa-ard, K; Dib, Claudio; Faessler, Amand; Gutsche, Thomas; Kovalenko, Sergey; Kuckei, Jan; Lyubovitskij, Valery E.; Pumsa-ard, Kem
2006-01-01
We calculate the electric dipole form factor of the neutron in a perturbative chiral quark model, parameterizing CP-violation of generic origin by means of effective electric dipole moments of the constituent quarks and their CP-violating couplings to the chiral fields. We discuss the relation of these effective parameters to more fundamental ones such as the intrinsic electric and chromoelectric dipole moments of quarks and the Weinberg parameter. From the existing experimental upper limits on the neutron EDM we derive constraints on these CP-violating parameters.
Covariant electromagnetic field lines
Hadad, Y.; Cohen, E.; Kaminer, I.; Elitzur, A. C.
2017-08-01
Faraday introduced electric field lines as a powerful tool for understanding the electric force, and these field lines are still used today in classrooms and textbooks teaching the basics of electromagnetism within the electrostatic limit. However, despite attempts at generalizing this concept beyond the electrostatic limit, such a fully relativistic field line theory still appears to be missing. In this work, we propose such a theory and define covariant electromagnetic field lines that naturally extend electric field lines to relativistic systems and general electromagnetic fields. We derive a closed-form formula for the field lines curvature in the vicinity of a charge, and show that it is related to the world line of the charge. This demonstrates how the kinematics of a charge can be derived from the geometry of the electromagnetic field lines. Such a theory may also provide new tools in modeling and analyzing electromagnetic phenomena, and may entail new insights regarding long-standing problems such as radiation-reaction and self-force. In particular, the electromagnetic field lines curvature has the attractive property of being non-singular everywhere, thus eliminating all self-field singularities without using renormalization techniques.
Chiral dynamics of baryons in the perturbative chiral quark model
Energy Technology Data Exchange (ETDEWEB)
Pumsa-ard, K.
2006-07-01
In this work we develop and apply variants of a perturbative chiral quark model (PCQM) to the study of baryonic properties dominantly in the low-energy region. In a first step we consider a noncovariant form of the PCQM, where confinement is modelled by a static, effective potential and chiral corrections are treated to second order, in line with similar chiral quark models. We apply the PCQM to the study of the electromagnetic form factors of the baryon octet. We focus in particular on the low-energy observables such as the magnetic moments, the charge and magnetic radii. In addition, the electromagnetic N-delta transition is also studied in the framework of the PCQM. In the chiral loop calculations we consider a quark propagator, which is restricted to the quark ground state, or in hadronic language to nucleon and delta intermediate states, for simplicity. We furthermore include the low-lying excited states to the quark propagator. In particular, the charge radius of the neutron and the transverse helicity amplitudes of the N-delta transition are considerably improved by this additional effect. In a next step we develop a manifestly Lorentz covariant version of the PCQM, where in addition higher order chiral corrections are included. The full chiral quark Lagrangian is motivated by and in analogy to the one of Chiral Perturbation Theory (ChPT). This Lagrangian contains a set of low energy constants (LECs), which are parameters encoding short distance effects and heavy degrees of freedom. We evaluate the chiral Lagrangian to order O(p{sup 4}) and to one loop to generate the dressing of the bare quark operators by pseudoscalar mesons. In addition we include the vector meson degrees of freedom in our study. Projection of the dressed quark operators on the baryonic level serves to calculate the relevant matrix elements. In a first application of this scheme, we resort to a parameterization of the valence quark form factors in the electromagnetic sector. Constraints
Strange quark matter and quark stars with the Dyson-Schwinger quark model
Chen, H.; Wei, J.-B.; Schulze, H.-J.
2016-09-01
We calculate the equation of state of strange quark matter and the interior structure of strange quark stars in a Dyson-Schwinger quark model within rainbow or Ball-Chiu vertex approximation. We emphasize constraints on the parameter space of the model due to stability conditions of ordinary nuclear matter. Respecting these constraints, we find that the maximum mass of strange quark stars is about 1.9 solar masses, and typical radii are 9-11km. We obtain an energy release as large as 3.6 × 10^{53} erg from conversion of neutron stars into strange quark stars.
Strange quark matter and quark stars with the Dyson-Schwinger quark model
Chen, H; Schulze, H -J
2016-01-01
We calculate the equation of state of strange quark matter and the interior structure of strange quark stars in a Dyson-Schwinger quark model within rainbow or Ball-Chiu vertex approximation. We emphasize constraints on the parameter space of the model due to stability conditions of ordinary nuclear matter. Respecting these constraints, we find that the maximum mass of strange quark stars is about 1.9 solar masses, and typical radii are 9--11 km. We obtain an energy release as large as $3.6 \\times 10^{53}\\,\\text{erg}$ from conversion of neutron stars into strange quark stars.
Strange quark matter and quark stars with the Dyson-Schwinger quark model
Energy Technology Data Exchange (ETDEWEB)
Chen, H.; Wei, J.B. [China University of Geosciences, School of Mathematics and Physics, Wuhan (China); Schulze, H.J. [Universita di Catania, Dipartimento di Fisica, Catania (Italy); INFN, Sezione di Catania (Italy)
2016-09-15
We calculate the equation of state of strange quark matter and the interior structure of strange quark stars in a Dyson-Schwinger quark model within rainbow or Ball-Chiu vertex approximation. We emphasize constraints on the parameter space of the model due to stability conditions of ordinary nuclear matter. Respecting these constraints, we find that the maximum mass of strange quark stars is about 1.9 solar masses, and typical radii are 9-11 km. We obtain an energy release as large as 3.6 x 10{sup 53} erg from conversion of neutron stars into strange quark stars. (orig.)
Instanton-dyon Ensembles III: Exotic Quark Flavors
Larsen, Rasmus
2016-01-01
"Exotic quarks" in the title refers to a modification of quark periodicity condition on the thermal circle by introduction of some phases -- known also as "flavor holonomies" -- different quark flavors. These phases provide a valuable tool, to be used for better understanding of deconfinement and chiral restoration phase transitions: by changing them one can dramatically modify both phase transitions. In the language of instanton constituents -- instanton-dyons or monopoles -- it has a very direct explanation: the interplay of flavor and color holonomies can switch topological zero modes between various dyon types. The model we will study in detail, the so called $Z_{N_c}$-symmetric QCD model with equal number of colors and flavors $N_c=N_f=2$ and special arrangement of flavor and color holonomies, ensure "most democratic" setting, in which each quark flavor and each dyon type are in one-to-one correspondence. The usual QCD has the opposite "most exclusive" arrangement: all quarks are antiperiodic and thus al...
Non-leptonic decays in an extended chiral quark model
Eeg, J O
2012-01-01
We consider the color suppressed (nonfactorizable) amplitude for the decay mode $\\bar{B_{d}^0} \\rightarrow \\pi^0 \\pi^{0} $. We treat the $b$-quark in the heavy quark limit and the energetic light ($u,d,s$) quarks within a variant of Large Energy Effective Theory combined with an extension of chiral quark models. Our calculated amplitude for $\\bar{B_{d}^0} \\rightarrow \\pi^0 \\pi^{0} $ is suppressed by a factor of order $\\Lambda_{QCD}/m_b$ with respect to the factorized amplitude, as it should according to QCD-factorization. Further, for reasonable values of the (model dependent) gluon condensate and the constituent quark mass, the calculated nonfactorizable amplitude for $\\bar{B_{d}^0} \\rightarrow \\pi^0 \\pi^{0} $ can easily accomodate the experimental value. Unfortunately, the color suppressed amplitude is very sensitive to the values of these model dependent parameters. Therefore fine-tuning is necessary in order to obtain an amplitude compatible with the experimental result for $\\bar{B_{d}^0} \\rightarrow \\pi^...
Two-solar-mass hybrid stars: a two model description with the Nambu-Jona-Lasinio quark model
Pereira, Renan Câmara; Providência, Constança
2016-01-01
Hybrid stars with a quark phase described by the Nambu$-$Jona-Lasinio model are studied. The hadron-quark model used to determine the stellar matter equation of state favors the appearance of quark matter: the coincidence of the deconfinement and chiral transitions and a low vacuum constituent quark mass. These two properties are essential to build equations of state that predict pure quark matter in the center of neutron stars. The effect of vector-isoscalar and vector-isovector terms is discussed, and it is shown that the vector-isoscalar terms are necessary to describe 2$M_\\odot$ hybrid stars, and the vector-isovector terms result in larger quark cores and a smaller deconfinement density.
SPECTRAL PROPERTIES OF QUARKS IN THE QUARK-GLUON PLASMA.
Energy Technology Data Exchange (ETDEWEB)
KARSCH,F.; KITAZAWA, M.
2007-07-30
We analyze the spectral properties of the quark propagator above the critical temperature for the deconfinement phase transition in quenched lattice QCD using clover improved Wilson fermions. The bare quark mass dependence of the quark spectral function is analyzed by varying the hopping parameter {kappa} in Landau gauge. We assume a two-pole structure for the quark spectral function, which is numerically found to work quite well for any value of {kappa}. It is shown that in the chiral limit the quark spectral function has two collective modes that correspond to the normal and plasmino excitations, while it is dominated by a single-pole structure when the bare quark mass becomes large.
Spectral Properties of Quarks in the Quark-Gluon Plasma
Karsch, F
2007-01-01
We analyze the spectral properties of the quark propagator above the critical temperature for the deconfinement phase transition in quenched lattice QCD using clover improved Wilson fermions. The bare quark mass dependence of the quark spectral function is analyzed by varying the hopping parameter \\kappa in Landau gauge. We assume a two-pole structure for the quark spectral function, which is numerically found to work quite well for any value of \\kappa. It is shown that in the chiral limit the quark spectral function has two collective modes that correspond to the normal and plasmino excitations, while it is dominated by a single-pole structure when the bare quark mass becomes large.
Bhatnagar, S; Bhatnagar, Shashank; Li, Shi-Yuan
2006-01-01
We employ the framework of Bethe-Salpeter equation under Covariant Instantaneous Ansatz (CIA) to study the leptonic decays of vector mesons. The calculations of decay constants f_v for rho, phi and omega mesons have been performed adopting a generalized structure of the hadron-quark vertex function Gamma which is generalized to include various Dirac covariants (other than the leading covariant i gamma cdot epsilon) from the complete set of covariants in accordance with a naive power counting rule, which allows the incorporation of them order by order in powers of the inverse of the meson mass.
Parametrization of Fully Dressed Quark Propagator
Institute of Scientific and Technical Information of China (English)
MA Wei-Xing; ZHU Ji-Zhen; ZHOU Li-Juan; SHEN Peng-Nian; HU Zhao-Hui
2005-01-01
Based on an extensive study of the Dyson-Schwinger equations for a fully dressed quark propagator in the "rainbow" approximation, a parametrized form of the quark propagator is suggested. The corresponding quark selfform of the quark propagator proposed in this work describes a confining quark propagation, and is quite convenient to be used in any numerical calculations.
The Multimedia Project Quarked!
Bean, Alice
2011-01-01
Can exposure to fundamental ideas about the nature of matter help motivate children in math and science and support the development of their understanding of these ideas later? Physicists, designers, and museum educators at the University of Kansas created the Quarked!(tm) Adventures in the subatomic Universe project to provide an opportunity for youth to explore the subatomic world in a fun and user friendly way. The project components include a website (located at http://www.quarked.org) and hands-on education programs. These are described and assessment results are presented. Questions addressed include the following. Can you engage elementary and middle school aged children with concepts related to particle physics? Can young children make sense of something they can't directly see? Do teachers think the material is relevant to their students?
Riordan, M
1992-05-29
Quarks are widely recognized today as being among the elementary particles of which matter is composed. The key evidence for their existence came from a series of inelastic electron-nucleon scattering experiments conducted between 1967 and 1973 at the Stanford Linear Accelerator Center. Other theoretical and experimental advances of the 1970s confirmed this discovery, leading to the present standard model of elementary particle physics.
Melting Hadrons, Boiling Quarks
Rafelski, Johann
2015-01-01
In the context of the Hagedorn temperature half-centenary I describe our understanding of the hot phases of hadronic matter both below and above the Hagedorn temperature. The first part of the review addresses many frequently posed questions about properties of hadronic matter in different phases, phase transition and the exploration of quark-gluon plasma (QGP). The historical context of the discovery of QGP is shown and the role of strangeness and strange antibaryon signature of QGP illustra...
Kane, Gordon L.; Perry, Malcolm J.
2015-03-01
We are used to thinking of quarks as fundamental particles in the same way we think of the electron, or gauge bosons, neutrinos, leptons. In strong theory, these objects are unified with gravitation and the physics of spacetime into what is hoped to be an ultimate theory, string/M theory. The string/M theory paradigm completely changes the way we think of the socalled elementary particles in quantum field theory.
Santopinto, E
2015-01-01
In this contribution, we briefly discuss the results for charmonium and bottomonium spectra with self-energy corrections in the unquenched quark model, due to the coupling to the meson-meson continuum. The UQM formalism can be extended to include also the effects of hybrid mesons, i.e. hybrid loops. Finally, we discuss the results of a calculation of hybrid mesons spectrum in Coulomb Gauge QCD.
Top quark pair production and top quark properties at CDF
Energy Technology Data Exchange (ETDEWEB)
Moon, Chang-Seong [INFN, Pisa
2016-06-02
We present the most recent measurements of top quark pairs production and top quark properties in proton-antiproton collisions with center-of-mass energy of 1.96 TeV using CDF II detector at the Tevatron. The combination of top pair production cross section measurements and the direct measurement of top quark width are reported. The test of Standard Model predictions for top quark decaying into $b$-quarks, performed by measuring the ratio $R$ between the top quark branching fraction to $b$-quark and the branching fraction to any type of down quark is shown. The extraction of the CKM matrix element $|V_{tb}|$ from the ratio $R$ is discussed. We also present the latest measurements on the forward-backward asymmetry ($A_{FB}$) in top anti-top quark production. With the full CDF Run II data set, the measurements are performed in top anti-top decaying to final states that contain one or two charged leptons (electrons or muons). In addition, we combine the results of the leptonic forward-backward asymmetry in $t\\bar t$ system between the two final states. All the results show deviations from the next-to-leading order (NLO) standard model (SM) calculation.
Nayak, Tapan; Sarkar, Sourav
2014-01-01
At extremely high temperatures and densities, protons and neutrons may dissolve into a "soup" of quarks and gluons, called the Quark-Gluon Plasma (QGP). For a few microseconds, shortly after the Big Bang, the Universe was filled with the QGP matter. The search and study of Quark-Gluon Plasma (QGP) is one of the most fundamental research topics of our times. The QGP matter has been probed by colliding heavy ions at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory, New York and the Large Hadron Collider at CERN, Geneva. By colliding heavy-ions at a speed close to that of light, scientists aim to obtain - albeit over a tiny volume of the size of a nucleus and for an infinitesimally short instant - a QGP state. This QGP state can be observed by dedicated experiments, as it reverts to hadronic matter through expansion and cooling. This volume presents some of the current theoretical and experimental understandings in the field of QGP.
Leibbrandt, G
2000-01-01
For pt.I see ibid., vol.440, p.537-602, 1995. The complete two-loop correction to the quark propagator, consisting of the spider, rainbow, gluon bubble and quark bubble diagrams, is evaluated in the non-covariant light-cone gauge (LCG), n.A/sup a/(x)=0, n/sup 2/=0. (The overlapping self-energy diagram had already been computed.) The chief technical tools include the powerful matrix integration technique, the n*/sub mu /-prescription for the spurious poles of (q.n)/sup -1/, and the detailed analysis of the boundary singularities in five- and six-dimensional parameter space. It is shown that the total divergent contribution to the two-loop correction Sigma /sub 2/ contains both covariant and non-covariant components, and is a local function of the external momentum p, even off the mass-shell, as all non-local divergent terms cancel exactly. Consequently, both the quark mass and field renormalizations are local. The structure of Sigma /sub 2/ implies a quark mass counterterm of the form delta m(LCG)=m alpha /sub...
Covariant representations of subproduct systems
Viselter, Ami
2010-01-01
A celebrated theorem of Pimsner states that a covariant representation $T$ of a $C^*$-correspondence $E$ extends to a $C^*$-representation of the Toeplitz algebra of $E$ if and only if $T$ is isometric. This paper is mainly concerned with finding conditions for a covariant representation of a \\emph{subproduct system} to extend to a $C^*$-representation of the Toeplitz algebra. This framework is much more general than the former. We are able to find sufficient conditions, and show that in important special cases, they are also necessary. Further results include the universality of the tensor algebra, dilations of completely contractive covariant representations, Wold decompositions and von Neumann inequalities.
Validity of Parametrized Quark Propagator
Institute of Scientific and Technical Information of China (English)
ZHUJi-Zhen; ZHOULi-Juan; MAWei-Xing
2005-01-01
Based on an extensively study of the Dyson-Schwinger equations for a fully dressed quark propagator in the “rainbow”approximation, a parametrized fully dressed quark propagator is proposed in this paper. The parametrized propagator describes a confining quark propagator in hadron since it is analytic everywhere in complex p2-plane and has no Lemmann representation. The validity of the new propagator is discussed by comparing its predictions on selfenergy functions A/(p2), Bl(p2) and effective mass M$(p2) of quark with flavor f to their corresponding theoretical results produced by Dyson-Schwinger equations. Our comparison shows that the parametrized quark propagator is a good approximation to the fully dressed quark propagator given by the solutions of Dyson-Schwinger equations in the rainbow approximation and is convenient to use in any theoretical calculations.
Validity of Parametrized Quark Propagator
Institute of Scientific and Technical Information of China (English)
ZHU Ji-Zhen; ZHOU Li-Juan; MA Wei-Xing
2005-01-01
Based on an extensively study of the Dyson-Schwinger equations for a fully dressed quark propagator in the "rainbow" approximation, a parametrized fully dressed quark propagator is proposed in this paper. The parametrized propagator describes a confining quark propagator in hadron since it is analytic everywhere in complex p2-plane and has no Lemmann representation. The validity of the new propagator is discussed by comparing its predictions on selfenergy functions Af(p2), Bf(p2) and effective mass Mf(p2) of quark with flavor f to their corresponding theoretical results produced by Dyson-Schwinger equations. Our comparison shows that the parametrized quark propagator is a good approximation to the fully dressed quark propagator given by the solutions of Dyson-Schwinger equations in the rainbow approximation and is convenient to use in any theoretical calculations.
String worldsheet for accelerating quark
Hubeny, Veronika E.; Semenoff, Gordon W.
2015-10-01
We consider the AdS bulk dual to an external massive quark in SYM following an arbitrary trajectory on Minkowski background. While a purely outgoing boundary condition on the gluonic field allows one to express the corresponding string worldsheet in a closed form, the setup has curious consequences. In particular, we argue that any quark whose trajectory on flat spacetime approaches that of a light ray in the remote past (as happens e.g. in the case of uniform acceleration) must necessarily be accompanied by an anti-quark. This is puzzling from the field theory standpoint, since one would expect that a sole quark following any timelike trajectory should be allowed. We explain the resolution in terms of boundary and initial conditions. We analyze the configuration in global AdS, which naturally suggests a modification to the boundary conditions allowing for a single accelerated quark without accompanying anti-quark. We contrast this resolution with earlier proposals.
Excitation rates of heavy quarks
Energy Technology Data Exchange (ETDEWEB)
Canal, C.A.G.; Santangelo, E.M.; Ducati, M.B.G.
1985-06-01
We obtain the production rates for c, b, and t quarks in deep-inelastic neutrino- (antineutrino-) nucleon interactions, in the standard six-quark model with left-handed couplings. The results are obtained with the most recent mixing parameters and we include a comparison between quark parametrizations. The excitations are calculated separately for each flavor, allowing the understanding of the role of threshold effects when considered through different rescaling variables.
Quark matter or new particles?
Michel, F. Curtis
1988-01-01
It has been argued that compression of nuclear matter to somewhat higher densities may lead to the formation of stable quark matter. A plausible alternative, which leads to radically new astrophysical scenarios, is that the stability of quark matter simply represents the stability of new particles compounded of quarks. A specific example is the SU(3)-symmetric version of the alpha particle, composed of spin-zero pairs of each of the baryon octet (an 'octet' particle).
Quark matter or new particles?
Michel, F. Curtis
1988-01-01
It has been argued that compression of nuclear matter to somewhat higher densities may lead to the formation of stable quark matter. A plausible alternative, which leads to radically new astrophysical scenarios, is that the stability of quark matter simply represents the stability of new particles compounded of quarks. A specific example is the SU(3)-symmetric version of the alpha particle, composed of spin-zero pairs of each of the baryon octet (an 'octet' particle).
Phenomenology of heavy quark systems
Energy Technology Data Exchange (ETDEWEB)
Gilman, F.J.
1987-03-01
The spectroscopy of heavy quark systems is examined with regards to spin independent and spin dependent potentials. It is shown that a qualitative picture exists of the spin-independent forces, and that a semi-quantitative understanding exists for the spin-dependent effects. A brief review is then given of the subject of the decays of hadrons containing heavy quarks, including weak decays at the quark level, and describing corrections to the spectator model. (LEW)
Exotic Signals of Vectorlike Quarks
Energy Technology Data Exchange (ETDEWEB)
Dobrescu, Bogdan A. [Fermilab; Yu, Felix [U. Mainz, PRISMA
2016-12-06
Vectorlike fermions are an important target for hadron collider searches. We show that the vectorlike quarks may predominantly decay via higher-dimensional operators into a quark plus a couple of other Standard Model fermions. Pair production of vectorlike quarks of charge 2/3 at the LHC would then lead to a variety of possible final states, including $t\\bar t + 4\\tau$, $t\\bar b\
Baryon properties and glueballs from Poincare-covariant bound-state equations
Sanchis-Alepuz, Helios
2012-01-01
In this thesis the covariant Bethe-Salpeter equation formalism is used to study some properties of ground-state baryons. This formalism relies on the knowledge of the interaction kernel among quarks and of the full quark propagator. For the interaction kernel, which is in principle a sum of infinitely many diagrams, I use the Ladder truncation. It amounts to reduce the interaction to a flavor-blind quark-mass independent vector-vector interaction between two quarks, mediated by a dressed gluon. The irreducible three-body interactions are neglected. The full quark propagator is obtained as a solution of the quark Dyson-Schwinger equation which is truncated such that, together with the truncation in the interaction kernel, chiral symmetry is correctly implemented. It is called Rainbow truncation, and together with the truncated kernel equation it constitutes the Rainbow-Ladder truncation of the Bethe-Salpeter equation. Any truncation induces the introduction of a model to account for the properties of the full ...
Antinori, Federico; Bass, Steffen A.; Bellwied, Rene; Ullrich, Thomas; Velkovska, Julia; Wiedemann, Urs
2005-04-01
Why another conference devoted to ultra-relativistic heavy-ion physics? As we looked around the landscape of the existing international conferences and workshops, we realized that there was not a single one tailored to the people who are most directly involved with the actual research work: students, post-docs, and junior faculty/research scientists. Of course there are schools, but that was not what we had in mind. We wanted a meeting where young researchers could come together to discuss in depth the physics that they are working on without any hindrance. The major conferences have very limited time for discussions which is often shared amongst the most established. This leaves little room for young people to ask their questions and to get the detailed feedback which they deserve and which satisfies their curiosity. A discussion-driven workshop, centering on those without whom there will be no future—that seemed like what was needed. And thus the Hot Quarks workshop was born. The aim of Hot Quarks was to enhance the direct exchange of scientific information among the younger members of the community, from both experiment and theory. Participation was by invitation only in order to emphasize the contributions from junior researchers. This approach makes the workshop unique among the many forums in the field. For young scientists it represented an opportunity for exposure that they would not have had in one of the major conferences. The hope is that this meeting has helped to stimulate the next generation of scientists in our field and, at the same time, strengthened their sense of community. It all came together from 18 24 July 2004, when the 77 participants met at The Inn at Snakedance in the Taos Ski Valley, New Mexico, USA, for the first Hot Quarks workshop. Photograph Participants gather in the sunshine at the foot of the Taos Ski Valley chairlift. By all accounts, Hot Quarks 2004 was a great success. Every participant had the opportunity to present her or
Top Quark Current Experimental Status
Juste, A
2006-01-01
Ten years after its discovery at the Tevatron collider, we still know little about the top quark. Its large mass suggests it may play a key role in the mechanism of Electroweak Symmetry Breaking (EWSB), or open a window of sensitivity to new physics related to EWSB and preferentially coupled to it. To determine whether this is the case, precision measurements of top quark properties are necessary. The high statistics samples being collected by the Tevatron experiments during Run II start to incisively probe the top quark sector. This report summarizes the experimental status of the top quark, focusing in particular on the recent measurements from the Tevatron.
Quark forces from hadronic spectroscopy.
Pirjol, Dan; Schat, Carlos
2009-04-17
We consider the implications of the most general two-body quark-quark interaction Hamiltonian for the spin-flavor structure of the negative parity L = 1 excited baryons. Assuming the most general two-body quark interaction Hamiltonian, we derive two correlations among the masses and mixing angles of these states, which constrain the mixing angles, and can be used to test for the presence of three-body quark interactions. We find that the pure gluon-exchange model is disfavored by data, independently of any assumptions about hadronic wave functions.
General covariance in computational electrodynamics
DEFF Research Database (Denmark)
Shyroki, Dzmitry; Lægsgaard, Jesper; Bang, Ole;
2007-01-01
We advocate the generally covariant formulation of Maxwell equations as underpinning some recent advances in computational electrodynamics—in the dimensionality reduction for separable structures; in mesh truncation for finite-difference computations; and in adaptive coordinate mapping as opposed...
Cold quark matter in compact stars
Energy Technology Data Exchange (ETDEWEB)
Franzon, B.; Fogaca, D. A.; Navarra, F. S. [Instituto de Fisica, Universidade de Sao Paulo Rua do Matao, Travessa R, 187, 05508-090 Sao Paulo, SP (Brazil); Horvath, J. E. [Instituto de Astronomia, Geofisica e Ciencias Atmosfericas, Universidade de Sao Paulo, Rua do Matao, 1226, 05508-090, Sao Paulo, SP (Brazil)
2013-03-25
We used an equation of state for the cold quark matter to the study of properties of quark stars. We also discuss the absolute stability of quark matter and compute the mass-radius relation for self-bound stars.
Plasmons in Anisotropic Quark-Gluon Plasma
Carrington, Margaret E; Mrowczynski, Stanislaw
2014-01-01
Plasmons of quark-gluon plasma - gluon collective modes - are systematically studied. The plasma is, in general, non-equilibrium but homogeneous. We consider anisotropic momentum distributions of plasma constituents which are obtained from the isotropic one by stretching or squeezing in one direction. This leads to prolate or oblate distributions, respectively. We study all possible degrees of one dimensional deformation from the extremely prolate case, when the momentum distribution is infinitely elongated in one direction, to the extremely oblate distribution, which is infinitely squeezed in the same direction. In between these extremes we discuss arbitrarily prolate, weakly prolate, isotropic, weakly oblate and arbitrarily oblate distributions. For each case, the number of modes is determined using a Nyquist analysis and the complete spectrum of plasmons is found analytically if possible, and numerically when not. Unstable modes are shown to exist in all cases except that of isotropic plasma. We derive con...
Valence quark and meson cloud contributions to the $\\gamma^\\ast N \\to N^\\ast(1520)$ form factors
Ramalho, G
2013-01-01
The covariant spectator quark model is applied to the $\\gamma^\\ast N \\to N^\\ast(1520)$ reaction. The valence quark contributions to the electromagnetic form factors and helicity transition amplitudes are estimated from the covariant structure of the $N^\\ast(1520)$ wave function calibrated by the experimental data for large squared momentum transfer $Q^2$. The difference between the model results and the experimental data is then used to parameterize the low $Q^2$ behavior, where meson cloud effects are assumed to dominate. This parametrization can be very useful for future studies of the reaction, as well as for the extension of the transition form factors to the timelike region.
The Discovery of the Top Quark
Sinervo, P.K.
1995-12-01
The top quark and the Higgs boson are the heaviest elementary particles predicted by the standard model. The four lightest quark flavours, the up, down, strange and charm quarks, were well-established by the mid-1970's. The discovery in 1977 of the {Tau} resonances, a new family of massive hadrons, required the introduction of the fifth quark flavour. Experimental and theoretical studies have indicated that this quark also has a heavier partner, the top quark.
Quark and Gluon Relaxation in Quark-Gluon Plasmas
Heiselberg, H.; Pethick, C. J.
1993-01-01
The quasiparticle decay rates for quarks and gluons in quark-gluon plasmas are calculated by solving the kinetic equation. Introducing an infrared cutoff to allow for nonperturbative effects, we evaluate the quasiparticle lifetime at momenta greater than the inverse Debye screening length to leading order in the coupling constant.
Quark and Gluon Relaxation in Quark-Gluon Plasmas
Heiselberg, H.; Pethick, C. J.
1993-01-01
The quasiparticle decay rates for quarks and gluons in quark-gluon plasmas are calculated by solving the kinetic equation. Introducing an infrared cutoff to allow for nonperturbative effects, we evaluate the quasiparticle lifetime at momenta greater than the inverse Debye screening length to leading order in the coupling constant.
Chiral symmetry and pi-pi scattering in the Covariant Spectator Theory
Biernat, Elmar P; Ribeiro, J E; Stadler, Alfred; Gross, Franz
2014-01-01
The pi-pi scattering amplitude calculated with a model for the quark-antiquark interaction in the framework of the Covariant Spectator Theory (CST) is shown to satisfy the Adler zero constraint imposed by chiral symmetry. The CST formalism is established in Minkowski space and our calculations are performed in momentum space. We prove that the axial-vector Ward-Takahashi identity is satisfied by our model. Then we show that, similarly to what happens within the Bethe-Salpeter formalism, application of the axial-vector Ward-Takahashi identity to the CST pi-pi scattering amplitude allows us to sum the intermediate quark-quark interactions to all orders. The Adler self-consistency zero for pi-pi scattering in the chiral limit emerges as the result for this sum.
Kurkela, Aleksi; Vuorinen, Aleksi
2016-07-22
We generalize the state-of-the-art perturbative equation of state of cold quark matter to nonzero temperatures, needed in the description of neutron star mergers and core collapse processes. The new result is accurate to O(g^{5}) in the gauge coupling, and is based on a novel framework for dealing with the infrared sensitive soft field modes of the theory. The zero Matsubara mode sector is treated via a dimensionally reduced effective theory, while the soft nonzero modes are resummed using the hard thermal loop approximation. This combination of known effective descriptions offers unprecedented access to small but nonzero temperatures, both in and out of beta equilibrium.
Kurkela, Aleksi
2016-01-01
We generalize the state-of-the-art perturbative Equation of State of cold quark matter to nonzero temperatures, needed in the description of neutron star mergers and core collapse processes. The new result is accurate to order g^5 in the gauge coupling, and is based on a novel framework for dealing with the infrared sensitive soft field modes of the theory. The zero Matsubara mode sector is treated using a dimensionally reduced effective theory, while the soft non-zero modes are resummed using the Hard Thermal Loop approximation. This combination of known effective descriptions offers unprecedented access to small but nonzero temperatures, both in and out of beta equilibrium.
Hard probes (and soft ones) to test the quark-gluon soup
Preuss, Paul
2006-01-01
"We need the hardest probes of all to study the hot, dense state of matter that exists when two heavy nuclei like gold collide with enough energy to temporarily free the quarks and gluons in their constituent protons and neutrons." (3 pages)
Energy Technology Data Exchange (ETDEWEB)
Déliot, Frédéric [IRFU, Saclay; Hadley, Nicholas [Maryland U., College Park; Parke, Stephen [Fermilab; Schwarz, Tom [Michigan U.
2014-10-01
The top quark is the heaviest known elementary particle, and it is often seen as a window to search for new physics processes in particle physics. A large program to study the top-quark properties has been performed both at the Tevatron and LHC colliders by the D0, CDF, ATLAS and CMS experiments. The most recent results are discussed in this article.
Heavy quark spectroscopy at LHCb
INSPIRE-00165164
2015-01-01
The analysis of $3.0 fb^{-1}$ of proton-proton collisions collected with the LHCb detector has yielded a broad range of results in spectroscopy of conventional and exotic hadrons with heavy quark(s) inside. We review the LHCb results which have been obtained over the last year.
Broniowski, Wojciech; Rybczynski, Maciej
2016-01-01
We review the results of the wounded quark model, with a stress on eccentricity observables in small systems. A new element is a presentation of symmetric cumulants for the elliptic and triangular flow correlations, obtained in the wounded-quark approach.
Gluon, Quark and Hadron Masses from a Modified Perturbative QCD
Rigol, M
2000-01-01
The development of a Modified Perturbation Theory for QCD, introduced in previous works, is continued. The gluon propagator is modified as consequence of a soft gluon pairs condensate in the vacuum. The modified Feynman rules for $\\alpha=1$ are shown, and some physical magnitudes calculated with them. The mean value of $G^{2}$, gluon masses and the effective potential are calculated up to the $g^2$ order, improving previous calculations. In connection with the gluon self-energy it follows that the gluonic mass shell becomes tachyonic in the considered approximation. The constituent quarks masses, produced by the influence of the condensate, are also calculated. Results of the order of 1/3 of the nucleon mass, are obtained for the constituent masses of the up and down quarks. In addition, the predicted flavour dependence of the calculated quarks masses turns out to be the appropriate to reproduce the spectrum of the ground states within the various groups of hadronic resonances, through the simple addition of ...
Calcul Stochastique Covariant à Sauts & Calcul Stochastique à Sauts Covariants
Maillard-Teyssier, Laurence
2003-01-01
We propose a stochastic covariant calculus forcàdlàg semimartingales in the tangent bundle $TM$ over a manifold $M$. A connection on $M$ allows us to define an intrinsic derivative ofa $C^1$ curve $(Y_t)$ in $TM$, the covariantderivative. More precisely, it is the derivative of$(Y_t)$ seen in a frame moving parallelly along its projection curve$(x_t)$ on $M$. With the transfer principle, Norris defined thestochastic covariant integration along a continuous semimartingale in$TM$. We describe t...
Covariate-free and Covariate-dependent Reliability.
Bentler, Peter M
2016-12-01
Classical test theory reliability coefficients are said to be population specific. Reliability generalization, a meta-analysis method, is the main procedure for evaluating the stability of reliability coefficients across populations. A new approach is developed to evaluate the degree of invariance of reliability coefficients to population characteristics. Factor or common variance of a reliability measure is partitioned into parts that are, and are not, influenced by control variables, resulting in a partition of reliability into a covariate-dependent and a covariate-free part. The approach can be implemented in a single sample and can be applied to a variety of reliability coefficients.
Levy Matrices and Financial Covariances
Burda, Zdzislaw; Jurkiewicz, Jerzy; Nowak, Maciej A.; Papp, Gabor; Zahed, Ismail
2003-10-01
In a given market, financial covariances capture the intra-stock correlations and can be used to address statistically the bulk nature of the market as a complex system. We provide a statistical analysis of three SP500 covariances with evidence for raw tail distributions. We study the stability of these tails against reshuffling for the SP500 data and show that the covariance with the strongest tails is robust, with a spectral density in remarkable agreement with random Lévy matrix theory. We study the inverse participation ratio for the three covariances. The strong localization observed at both ends of the spectral density is analogous to the localization exhibited in the random Lévy matrix ensemble. We discuss two competitive mechanisms responsible for the occurrence of an extensive and delocalized eigenvalue at the edge of the spectrum: (a) the Lévy character of the entries of the correlation matrix and (b) a sort of off-diagonal order induced by underlying inter-stock correlations. (b) can be destroyed by reshuffling, while (a) cannot. We show that the stocks with the largest scattering are the least susceptible to correlations, and likely candidates for the localized states. We introduce a simple model for price fluctuations which captures behavior of the SP500 covariances. It may be of importance for assets diversification.
Can sea quark asymmetry shed light on the orbital angular momentum of the proton?
Nocera, Emanuele R
2016-01-01
A striking prediction of several extensions of the constituent quark model, including the unquenched quark model, the pion cloud model and the chiral quark model, is a proportionality relationship between the quark sea asymmetry and the orbital angular momentum of the proton. We investigate to which extent a relationship of this kind is corroborated by the experiment, through a systematic comparison between expectations based on models and predictions obtained from a global analysis of hard-scattering data in perturbative Quantum Chromodynamics. We find that the data allows the angular momentum of the proton to be proportional to its sea asymmetry, though with a rather large range of the optimal values of the proportionality coefficient. Typical values do not enable us to discriminate among expectations based on different models. In order to make our comparison conclusive, the extrapolation uncertainties on the proportionality coefficient should be reduced, hopefully by means of accurate measurements in the r...
Relativistic three-body quark model of light baryons based on hypercentral approach
Aslanzadeh, M.; Rajabi, A. A.
2015-05-01
In this paper, we have treated the light baryons as a relativistic three-body bound system. Inspired by lattice QCD calculations, we treated baryons as a spin-independent three-quark system within a relativistic three-quark model based on the three-particle Klein-Gordon equation. We presented the analytical solution of three-body Klein-Gordon equation with employing the constituent quark model based on a hypercentral approach through which two- and three-body forces are taken into account. Herewith the average energy values of the up, down and strange quarks containing multiplets are reproduced. To describe the hyperfine structure of the baryon, the splittings within the SU(6)-multiplets are produced by the generalized Gürsey Radicati mass formula. The considered SU(6)-invariant potential is popular "Coulomb-plus-linear" potential and the strange and non-strange baryons spectra are in general well reproduced.
On diquark clustering in quark-gluon plasma
Indian Academy of Sciences (India)
A K Sisodiya; V S Bhasin; R S Kaushal
2006-02-01
The possibility that pairs of quarks will form diquark clusters in the regime above deconfinement transition for hadron matter at finite density is revisited. Here we present the results on the diquark-diquark (dq-dq) interaction in the framework of constituent quark model taking account of spin, isospin and color degrees of freedom in the spirit of generalized Pauli principle. By constructing the appropriate spin and color states of the dq-dq clusters we compute the expectation values of the interaction Hamiltonian involving pairwise quark-quark interaction. We find that the effective interaction between two diquark clusters is quite sensitive to different configurations characterized by color and spin states, obtained after the coupling of two diquark states. The value of the coupling parameter for a particular color-spin state, i.e., $\\{\\bar{3}, 1\\}$ is compared to the one obtained earlier by Donoghue and Sateesh, Phys. Rev. D38, 360 (1988) based on the effective 4-theory. This new value of derived for different color-spin dq-dq states, may lead to several important implications in the studies of diquark star and diquark gas.
Semileptonic Decays of Heavy Omega Baryons in a Quark Model
Pervin, M; Capstick, S; Pervin, Muslema
2006-01-01
The semileptonic decays of $\\Omega_c$ and $\\Omega_b$ are treated in the framework of a constituent quark model developed in a previous paper on the semileptonic decays of heavy $\\Lambda$ baryons. Analytic results for the form factors for the decays to ground states and a number of excited states are evaluated. For $\\Omega_b$ to $\\Omega_c$ the form factors obtained are shown to satisfy the relations predicted at leading order in the heavy-quark effective theory at the non-recoil point. A modified fit of nonrelativistic and semirelativistic Hamiltonians generates configuration-mixed baryon wave functions from the known masses and the measured $\\lcle$ rate, with wave functions expanded in both harmonic oscillator and Sturmian bases. Decay rates of $\\ob$ to pairs of ground and excited $\\omc$ states related by heavy-quark symmetry calculated using these configuration-mixed wave functions are in the ratios expected from heavy-quark effective theory, to a good approximation. Our predictions for the semileptonic elas...
Jan-e~Alam; Subhasis~Chattopadhyay; Tapan~Nayak
2008-10-01
Quark Matter 2008—the 20th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions was held in Jaipur, the Pink City of India, from 4-10 February, 2008. Organizing Quark Matter 2008 in India itself indicates the international recognition of the Indian contribution to the field of heavy-ion physics, which was initiated and nurtured by Bikash Sinha, Chair of the conference. The conference was inaugurated by the Honourable Chief Minister of Rajasthan, Smt. Vasundhara Raje followed by the key note address by Professor Carlo Rubbia. The scientific programme started with the theoretical overview, `SPS to RHIC and onwards to LHC' by Larry McLerran followed by several theoretical and experimental overview talks on the ongoing experiments at SPS and RHIC. The future experiments at the LHC, FAIR and J-PARC, along with the theoretical predictions, were discussed in great depth. Lattice QCD predictions on the nature of the phase transition and critical point were vigorously debated during several plenary and parallel session presentations. The conference was enriched by the presence of an unprecedented number of participants; about 600 participants representing 31 countries across the globe. This issue contains papers based on plenary talks and oral presentations presented at the conference. Besides invited and contributed talks, there were also a large number of poster presentations. Members of the International Advisory Committee played a pivotal role in the selection of speakers, both for plenary and parallel session talks. The contributions of the Organizing Committee in all aspects, from helping to prepare the academic programme down to arranging local hospitality, were much appreciated. We thank the members of both the committees for making Quark Matter 2008 a very effective and interesting platform for scientific deliberations. Quark Matter 2008 was financially supported by: Air Liquide (New Delhi) Board of Research Nuclear Sciences (Mumbai) Bose
Linear Landau damping in strongly relativistic quark gluon plasma
Energy Technology Data Exchange (ETDEWEB)
Murtaza, G.; Khattak, N.A.D.; Shah, H.A. [Salam Chair in Physics, G C Univ., Lahore (Pakistan)]|[Dept. of Physics, G C Univ., Lahore (Pakistan)
2004-07-01
On the basis of semi classical kinetic Vlasov equation for Quark-Gluon plasma (QGP) and Yang-Mills equation in covariant gauge, linear Landau damping for electrostatic perturbations like Langmuir waves is investigated. For the extreme relativistic case, wherein the thermal speed of the particles exceeds the phase velocity of the perturbations, the linear Landau damping is absent. However, a departure from extreme relativistic case generates an imaginary component of the frequency giving rise to linear Landau damping effect. The relevant integral for the conductivity tensor has been evaluated and the dispersion relation for the longitudinal part of the oscillation obtained. (orig.)
Szekeres models: a covariant approach
Apostolopoulos, Pantelis S
2016-01-01
We exploit the 1+1+2 formalism to covariantly describe the inhomogeneous and anisotropic Szekeres models. It is shown that an \\emph{average scale length} can be defined \\emph{covariantly} which satisfies a 2d equation of motion driven from the \\emph{effective gravitational mass} (EGM) contained in the dust cloud. The contributions to the EGM are encoded to the energy density of the dust fluid and the free gravitational field $E_{ab}$. In addition the notions of the Apparent and Absolute Apparent Horizons are briefly discussed and we give an alternative gauge-invariant form to define them in terms of the kinematical variables of the spacelike congruences. We argue that the proposed program can be used in order to express the Sachs optical equations in a covariant form and analyze the confrontation of a spatially inhomogeneous irrotational overdense fluid model with the observational data.
Multivariate covariance generalized linear models
DEFF Research Database (Denmark)
Bonat, W. H.; Jørgensen, Bent
2016-01-01
We propose a general framework for non-normal multivariate data analysis called multivariate covariance generalized linear models, designed to handle multivariate response variables, along with a wide range of temporal and spatial correlation structures defined in terms of a covariance link...... function combined with a matrix linear predictor involving known matrices. The method is motivated by three data examples that are not easily handled by existing methods. The first example concerns multivariate count data, the second involves response variables of mixed types, combined with repeated...... are fitted by using an efficient Newton scoring algorithm based on quasi-likelihood and Pearson estimating functions, using only second-moment assumptions. This provides a unified approach to a wide variety of types of response variables and covariance structures, including multivariate extensions...
Covariance evaluation work at LANL
Energy Technology Data Exchange (ETDEWEB)
Kawano, Toshihiko [Los Alamos National Laboratory; Talou, Patrick [Los Alamos National Laboratory; Young, Phillip [Los Alamos National Laboratory; Hale, Gerald [Los Alamos National Laboratory; Chadwick, M B [Los Alamos National Laboratory; Little, R C [Los Alamos National Laboratory
2008-01-01
Los Alamos evaluates covariances for nuclear data library, mainly for actinides above the resonance regions and light elements in the enUre energy range. We also develop techniques to evaluate the covariance data, like Bayesian and least-squares fitting methods, which are important to explore the uncertainty information on different types of physical quantities such as elastic scattering angular distribution, or prompt neutron fission spectra. This paper summarizes our current activities of the covariance evaluation work at LANL, including the actinide and light element data mainly for the criticality safety study and transmutation technology. The Bayesian method based on the Kalman filter technique, which combines uncertainties in the theoretical model and experimental data, is discussed.
Clustered Quark Matter Calculation for Strange Quark Matter
Na, Xuesen
2009-01-01
Motivated by the need for a solid state strange quark matter to better explain some observational phenomena, we discussed possibility of color singlet cluster formation in cold strange quark matter by a rough calculation following the excluded volume method proposed by Clark et al (1986) and adopted quark mass density dependent model with cubic scaling. It is found that 70% to 75% of volume and 80% to 90% of baryon number is in clusters at temperature from 10MeV to 50MeV and 1 to 10 times nuclear density.
Cosmic Censorship Conjecture revisited: Covariantly
Hamid, Aymen I M; Maharaj, Sunil D
2014-01-01
In this paper we study the dynamics of the trapped region using a frame independent semi-tetrad covariant formalism for general Locally Rotationally Symmetric (LRS) class II spacetimes. We covariantly prove some important geometrical results for the apparent horizon, and state the necessary and sufficient conditions for a singularity to be locally naked. These conditions bring out, for the first time in a quantitative and transparent manner, the importance of the Weyl curvature in deforming and delaying the trapped region during continual gravitational collapse, making the central singularity locally visible.
Evidence for production of single top quarks
Abazov, V.M.; et al., [Unknown; de Jong, S.J.; Demarteau, M.; Houben, P.; van den Berg, P.J.
2008-01-01
We present first evidence for the production of single top quarks in the D0 detector at the Fermilab Tevatron p (p) over bar collider. The standard model predicts that the electroweak interaction can produce a top quark together with an antibottom quark or light quark, without the antiparticle top-q
Top Quark Properties Measurements in CMS
Yazgan, Efe
Recent top quark properties measurements made with the CMS detector at the LHC are presented. The measurements summarized include spin correlation of top quark pairs, asymmetries, top quark mass, and the underlying event in top quark pair events. The results are compared to the standard model predictions and new physics models.
Top quark properties at ATLAS and CMS
Brock, Ian; The ATLAS collaboration
2016-01-01
Recent results from ATLAS and CMS connected to the properties of the top quark are presented. The talk concentrates on asymmetries connected with top-quark production and the measurement of spin correlations between the top quark and antiquark. A search for CP violation in top-quark-antiquark production is also discussed.
Top quark properties measurements in CMS
Yazgan, E.; CMS Collaboration
2017-07-01
Recent top quark properties measurements made with the CMS detector at the LHC are presented. The measurements summarized include spin correlation of top quark pairs, asymmetries, top quark mass, and the underlying event in top quark pair events. The results are compared to the standard model predictions and new physics models.
Chemical constituents of Asparagus
Directory of Open Access Journals (Sweden)
J S Negi
2010-01-01
Full Text Available Asparagus species (family Liliaceae are medicinal plants of temperate Himalayas. They possess a variety of biological properties, such as being antioxidants, immunostimulants, anti-inflammatory, antihepatotoxic, antibacterial, antioxytocic, and reproductive agents. The article briefly reviews the isolated chemical constituents and the biological activities of the plant species. The structural formula of isolated compounds and their distribution in the species studied are also given.
Radiative leptonic Bc decay in the relativistic independent quark model
Barik, N.; Naimuddin, Sk.; Dash, P. C.; Kar, Susmita
2008-12-01
The radiative leptonic decay Bc-→μ-ν¯μγ is analyzed in its leading order in a relativistic independent quark model based on a confining potential in an equally mixed scalar-vector harmonic form. The branching ratio for this decay in the vanishing lepton mass limit is obtained as Br(Bc→μνμγ)=6.83×10-5, which includes the contributions of the internal bremsstrahlung and structure-dependent diagrams at the level of the quark constituents. The contributions of the bremsstrahlung and the structure-dependent diagrams, as well as their additive interference parts, are compared and found to be of the same order of magnitude. Finally, the predicted photon energy spectrum is observed here to be almost symmetrical about the peak value of the photon energy at Ẽγ≃(MBc)/(4), which may be quite accessible experimentally at LHC in near future.
Color Instabilities in the Quark-Gluon Plasma
Mrowczynski, Stanislaw; Strickland, Michael
2016-01-01
When the quark-gluon plasma (QGP) - a system of deconfined quarks and gluons - is in a nonequilibrium state, it is usually unstable with respect to color collective modes. The instabilities, which are expected to strongly influence dynamics of the QGP produced in relativistic heavy-ion collisions, are extensively discussed under the assumption that the plasma is weakly coupled. We begin by presenting the theoretical approaches to study the QGP, which include: field theory methods based on the Keldysh-Schwinger formalism, classical and kinetic theories, and fluid techniques. The dispersion equations, which give the spectrum of plasma collective excitations, are analyzed in detail. Particular attention is paid to a momentum distribution of plasma constituents which is obtained by deforming an isotropic momentum distribution. Mechanisms of chromoelectric and chromomagnetic instabilities are explained in terms of elementary physics. The Nyquist analysis, which allows one to determine the number of solutions of a ...
Nonperturbative equation of state of quark gluon plasma: Applications
Komarov, E. V.; Simonov, Yu. A.
2008-05-01
The vacuum-driven nonperturbative factors Li for quark and gluon Green's functions are shown to define the nonperturbative dynamics of QGP in the leading approximation. EoS obtained recently in the framework of this approach is compared in detail with known lattice data for μ = 0 including P/ T4, ɛ/ T4, {ɛ-3P}/{T4}. The basic role in the dynamics at T ≲ 3 Tc is played by the factors Li which are approximately equal to the modulus of Polyakov line for quark Lfund and gluon Ladj. The properties of Li are derived from field correlators and compared to lattice data, in particular the Casimir scaling property Ladj=(Lfund) follows in the Gaussian approximation valid for small vacuum correlation lengths. Resulting curves for P/ T4, ɛ/ T4, {ɛ-3P}/{T4} are in a reasonable agreement with lattice data, the remaining difference points out to an effective attraction among QGP constituents.
A covariant model of the electromagnetic current for the study of two-body scalar systems
Acero, M A; Sandoval, C E; Sanctis, Maurizio De; Sandoval, Carlos E.
2005-01-01
We present a procedure to derive a covariant electromagnetic current operator for a system made up by two scalars constituents. Using different wave functions we fitted their parameters to the experimental data of the pion form factor, obtainig great discrepancy at low momentum transfer. Introducing the Vector Meson Dominance corrective factor, we obtained a better fit to the data.
Valence quark contributions for the gamma N -> P11(1440) form factors
Ramalho, G
2010-01-01
Using a covariant spectator quark model we estimate valence quark contributions to the F1*(Q2) and F2*(Q2) transition form factors for the gamma N -> P11(1440) reaction. The Roper resonance, P11(1440), is assumed to be the first radial excitation of the nucleon. The present model requires no extra parameters except for those already fixed by the previous studies for the nucleon. Our results are consistent with the experimental data in the high Q2 region, and those from lattice QCD. We also estimate the meson cloud contributions, focusing on the low Q2 region, where they are expected to be dominant.
Valence quark contributions for the gamma N -> P11(1440) transition
Energy Technology Data Exchange (ETDEWEB)
G. Ramalho, K. Tsushima
2011-03-01
A covariant spectator quark model is applied to estimate the valence quark contributions to the$ F1*(Q2) and F2*(Q2) transition form factors for the gamma N -> P11(1440) reaction. The Roper resonance, P11(1440), is assumed to be the first radial excitation of the nucleon. The model requires no extra parameters except for those already fixed by the previous studies for the nucleon. The results are consistent with the experimental data in the high Q2 region, and those from the lattice QCD. Finally the model is also applied to estimate the meson cloud contributions from the CLAS and MAID analysis.
Valence quark contributions for the gamma N -> P11(1440) transition
Ramalho, G
2010-01-01
A covariant spectator quark model is applied to estimate the valence quark contributions to the$ F1*(Q2) and F2*(Q2) transition form factors for the gamma N -> P11(1440) reaction. The Roper resonance, P11(1440), is assumed to be the first radial excitation of the nucleon. The model requires no extra parameters except for those already fixed by the previous studies for the nucleon. The results are consistent with the experimental data in the high Q2 region, and those from the lattice QCD. Finally the model is also applied to estimate the meson cloud contributions from the CLAS and MAID analysis.
Exact duality and Bjorken sum rule in heavy quark models à la Bakamjian-Thomas
Le Yaouanc, A; Pène, O; Raynal, J C
1996-01-01
The heavy mass limit of quark models based on the Bakamjian-Thomas cons\\-truction reveals remarkable features. In addition to previously demonstrated properties of covariance and Isgur-Wise scaling, exact duality, leading to the Bjorken-Isgur-Wise sum rule, is proven, for the first time to our knowledge in relativistic quark models. Inelastic as well as elastic contributions to the sum rule are then discussed in terms of ground state averages of a few number of operators corresponding to the nonrelativistic dipole operator and various relativistic corrections.
Quark Virtuality and QCD Vacuum Condensates
Institute of Scientific and Technical Information of China (English)
ZHOU Li-Juan; MA Wei-Xing
2004-01-01
@@ Based on the Dyson-Schwinger equations (DSEs) in the ‘rainbow' approximation, we investigate the quark virtuality in the vacuum state and quantum-chromodynamics (QCD) vacuum condensates. In particular, we calculate the local quark vacuum condensate and quark-gluon mixed condensates, and then the virtuality of quark. The calculated quark virtualities are λ2u,d = 0.7 GeV2 for u, d quarks, and 2s 1.6 GeV2 for s quark.Our theoretical predictions are consistent with empirical values used in QCD sum rules, and also fit to lattice QCD predictions.
Top quark studies at hadron colliders
Energy Technology Data Exchange (ETDEWEB)
Sinervo, P.K. [Univ. of Toronto, Ontario (Canada)
1997-01-01
The techniques used to study top quarks at hadron colliders are presented. The analyses that discovered the top quark are described, with emphasis on the techniques used to tag b quark jets in candidate events. The most recent measurements of top quark properties by the CDF and DO Collaborations are reviewed, including the top quark cross section, mass, branching fractions, and production properties. Future top quark studies at hadron colliders are discussed, and predictions for event yields and uncertainties in the measurements of top quark properties are presented.
Energy Technology Data Exchange (ETDEWEB)
Menzione, A. [INFN Sezione di Pisa (Italy)
1995-10-01
Most of the material presented in this report, comes from contributions to the parallel session PL20 of this conference. We summarise the experimental results of direct production of Top quarks, coming from the CDF and C0 Collaborations at Fermilab, and compare these results to what one expects within current theoretical understanding. Particular attention is given to new results such as all hadronic modes of t{bar t} decay. As far as the mass is concerned, a comparison is made with precision measurements of related quantities, coming from LEP and other experiments. An attempt is made to look at the medium-term future and understand which variables and with what accuracy one can measure them with increased integrated luminosity.
Melting Hadrons, Boiling Quarks
Rafelski, Johann
2015-01-01
In the context of the Hagedorn temperature half-centenary I describe our understanding of the hot phases of hadronic matter both below and above the Hagedorn temperature. The first part of the review addresses many frequently posed questions about properties of hadronic matter in different phases, phase transition and the exploration of quark-gluon plasma (QGP). The historical context of the discovery of QGP is shown and the role of strangeness and strange antibaryon signature of QGP illustrated. In the second part I discuss the corresponding theoretical ideas and show how experimental results can be used to describe the properties of QGP at hadronization. Finally in two appendices I present previously unpublished reports describing the early prediction of the different forms of hadron matter and of the formation of QGP in relativistic heavy ion collisions, including the initial prediction of strangeness and in particular strange antibaryon signature of QGP.
Melting hadrons, boiling quarks
Energy Technology Data Exchange (ETDEWEB)
Rafelski, Johann [CERN-PH/TH, Geneva 23 (Switzerland); The University of Arizona, Department of Physics, Tucson, Arizona (United States)
2015-09-15
In the context of the Hagedorn temperature half-centenary I describe our understanding of the hot phases of hadronic matter both below and above the Hagedorn temperature. The first part of the review addresses many frequently posed questions about properties of hadronic matter in different phases, phase transition and the exploration of quark-gluon plasma (QGP). The historical context of the discovery of QGP is shown and the role of strangeness and strange antibaryon signature of QGP illustrated. In the second part I discuss the corresponding theoretical ideas and show how experimental results can be used to describe the properties of QGP at hadronization. The material of this review is complemented by two early and unpublished reports containing the prediction of the different forms of hadron matter, and of the formation of QGP in relativistic heavy ion collisions, including the discussion of strangeness, and in particular strange antibaryon signature of QGP. (orig.)
Thorndike, Edward H.; Poling, Ronald A.
1988-01-01
Recent experimental results on the decay of b-flavored hadrons are reviewed. Substantial progress has been made in the study of exclusive and inclusive B-meson decays, as well as in the theoretical understanding of these processes. The two most prominent developments are the continuing failure to observe evidence of decays of the b quark to a u quark rather than a c quark, and the surprisingly high level of B 0- overlineB0 mi xing which has recently been reported by the ARGUS collaboration. Notwithstanding these results, we conclude that the health of the Standard Model is excellent.
Covariant effective action for a Galilean invariant quantum Hall system
Geracie, Michael; Prabhu, Kartik; Roberts, Matthew M.
2016-09-01
We construct effective field theories for gapped quantum Hall systems coupled to background geometries with local Galilean invariance i.e. Bargmann spacetimes. Along with an electromagnetic field, these backgrounds include the effects of curved Galilean spacetimes, including torsion and a gravitational field, allowing us to study charge, energy, stress and mass currents within a unified framework. A shift symmetry specific to single constituent theories constraints the effective action to couple to an effective background gauge field and spin connection that is solved for by a self-consistent equation, providing a manifestly covariant extension of Hoyos and Son's improvement terms to arbitrary order in m.
Covariant description of isothermic surfaces
Tafel, Jacek
2014-01-01
We present a covariant formulation of the Gauss-Weingarten equations and the Gauss-Mainardi-Codazzi equations for surfaces in 3-dimensional curved spaces. We derive a coordinate invariant condition on the first and second fundamental form which is necessary and sufficient for the surface to be isothermic.
Condition Number Regularized Covariance Estimation.
Won, Joong-Ho; Lim, Johan; Kim, Seung-Jean; Rajaratnam, Bala
2013-06-01
Estimation of high-dimensional covariance matrices is known to be a difficult problem, has many applications, and is of current interest to the larger statistics community. In many applications including so-called the "large p small n" setting, the estimate of the covariance matrix is required to be not only invertible, but also well-conditioned. Although many regularization schemes attempt to do this, none of them address the ill-conditioning problem directly. In this paper, we propose a maximum likelihood approach, with the direct goal of obtaining a well-conditioned estimator. No sparsity assumption on either the covariance matrix or its inverse are are imposed, thus making our procedure more widely applicable. We demonstrate that the proposed regularization scheme is computationally efficient, yields a type of Steinian shrinkage estimator, and has a natural Bayesian interpretation. We investigate the theoretical properties of the regularized covariance estimator comprehensively, including its regularization path, and proceed to develop an approach that adaptively determines the level of regularization that is required. Finally, we demonstrate the performance of the regularized estimator in decision-theoretic comparisons and in the financial portfolio optimization setting. The proposed approach has desirable properties, and can serve as a competitive procedure, especially when the sample size is small and when a well-conditioned estimator is required.
Condition Number Regularized Covariance Estimation*
Won, Joong-Ho; Lim, Johan; Kim, Seung-Jean; Rajaratnam, Bala
2012-01-01
Estimation of high-dimensional covariance matrices is known to be a difficult problem, has many applications, and is of current interest to the larger statistics community. In many applications including so-called the “large p small n” setting, the estimate of the covariance matrix is required to be not only invertible, but also well-conditioned. Although many regularization schemes attempt to do this, none of them address the ill-conditioning problem directly. In this paper, we propose a maximum likelihood approach, with the direct goal of obtaining a well-conditioned estimator. No sparsity assumption on either the covariance matrix or its inverse are are imposed, thus making our procedure more widely applicable. We demonstrate that the proposed regularization scheme is computationally efficient, yields a type of Steinian shrinkage estimator, and has a natural Bayesian interpretation. We investigate the theoretical properties of the regularized covariance estimator comprehensively, including its regularization path, and proceed to develop an approach that adaptively determines the level of regularization that is required. Finally, we demonstrate the performance of the regularized estimator in decision-theoretic comparisons and in the financial portfolio optimization setting. The proposed approach has desirable properties, and can serve as a competitive procedure, especially when the sample size is small and when a well-conditioned estimator is required. PMID:23730197
Covariation Neglect among Novice Investors
Hedesstrom, Ted Martin; Svedsater, Henrik; Garling, Tommy
2006-01-01
In 4 experiments, undergraduates made hypothetical investment choices. In Experiment 1, participants paid more attention to the volatility of individual assets than to the volatility of aggregated portfolios. The results of Experiment 2 show that most participants diversified even when this increased risk because of covariation between the returns…
Energy Technology Data Exchange (ETDEWEB)
Wicke, Daniel; /Wuppertal U., Dept. Math.
2009-08-01
The aim of particle physics is the understanding of elementary particles and their interactions. The current theory of elementary particle physics, the Standard Model, contains twelve different types of fermions which (neglecting gravity) interact through the gauge bosons of three forces. In addition a scalar particle, the Higgs boson, is needed for theoretical consistency. These few building blocks explain all experimental results found in the context of particle physics, so far. Nevertheless, it is believed that the Standard Model is only an approximation to a more complete theory. First of all the fourth known force, gravity, has withstood all attempts to be included until now. Furthermore, the Standard Model describes several features of the elementary particles like the existence of three families of fermions or the quantisation of charges, but does not explain these properties from underlying principles. Finally, the lightness of the Higgs boson needed to explain the symmetry breaking is difficult to maintain in the presence of expected corrections from gravity at high scales. This is the so called hierarchy problem. In addition astrophysical results indicate that the universe consists only to a very small fraction of matter described by the Standard Model. Large fractions of dark energy and dark matter are needed to describe the observations. Both do not have any correspondence in the Standard Model. Also the very small asymmetry between matter and anti-matter that results in the observed universe built of matter (and not of anti-matter) cannot be explained until now. It is thus an important task of experimental particle physics to test the predictions of the Standard Model to the best possible accuracy and to search for deviations pointing to necessary extensions or modifications of our current theoretical understanding. The top quark was predicted to exist by the Standard Model as the partner of the bottom quark. It was first observed in 1995 by the
Quasiparticle properties of the quarks of the Nambu-Jona-Lasinio model
Cao, Nan-Wei; Shakin, C. M.; Sun, Wei-Dong
1992-12-01
In spite of the apparent limitations of the model, in recent years there have been many applications of the Nambu-Jona-Lasinio (NJL) model in the study of hadron structure and in the study of the behavior of nuclear matter at finite temperature and density. A number of researchers have studied a generalized SU(3) version of the NJL model. For example, Vogl, Lutz, Klimt, and Weise [Nucl. Phys. A516 469 (1990)] have performed extensive calculations that include a calculation of a scalar form factor of a constituent quark, Fs(q2), and a calculation of a quark sigma term σq. (In their work, the latter quantity is related to the nucleon sigma term σN as in a constituent quark model: σN=3σq.) These calculations are made in what may be termed a sigma-dominance approximation. In the work reported here, we review the important role played by the nucleon sigma term in understanding the behavior of the quark condensate in the presence of matter. We make use of the original SU(2) version of the NJL model to study how various quark properties are modified when we take into account the dressing of the constituent quarks by the pion, the Goldstone boson of the model. We calculate the quark self-energy arising from emission and absorption of a pion and also show how the calculation of the scalar form factor of the quark and σq are modified due to the coupling of the quark to the pion. The correction terms considered here serve to reduce the value of σq by a small amount relative to the value obtained in the simplest version of the sigma dominance model. For example, for a Euclidean momentum cutoff, Λ=1050 MeV, the uncorrected result is σN=54.6 MeV. That value is then reduced to σN=51.5 MeV, if the corrections due to the pion ``dressing'' are included. It is also found that the residue at the quasiparticle pole of the quark propagator Z is about 0.86 when the coupling to the pion field is taken into account.
Holographic quark-gluon plasmas at finite quark density
Energy Technology Data Exchange (ETDEWEB)
Bigazzi, F. [Dipartimento di Fisica e Astronomia, Universita di Firenze, Sesto Fiorentino (Firenze), Pisa (Italy); INFN, Sezione di Torino (Italy); Cotrone, A. [Dipartimento di Fisica, Universita di Torino (Italy); Mas, J. [Departamento de Fisica de Particulas, Universidade de Santiago de Compostela (Spain); Instituto Galego de Fisica de Altas Enerxias (IGFAE), Santiago de Compostela (Spain); Tarrio, J. [Institute for Theoretical Physics and Spinoza Institute, Universiteit Utrecht, 3584 CE, Utrecht (Netherlands); Mayerson, D. [Institute for Theoretical Physics, University of Amsterdam (Netherlands)
2012-07-15
Gravity solutions holographically dual to strongly coupled quark-gluon plasmas with non-zero quark density are reviewed. They are motivated by the urgency of finding novel tools to explore the phase diagram of QCD-like theories at finite chemical potential. After presenting the solutions and their regime of validity, some of their physical properties are discussed. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Quark-anti-quark potential in N = 4 SYM
Gromov, Nikolay; Levkovich-Maslyuk, Fedor
2016-12-01
We construct a closed system of equations describing the quark-anti-quark potential at any coupling in planar N = 4 supersymmetric Yang-Mills theory. It is based on the Quantum Spectral Curve method supplemented with a novel type of asymptotics. We present a high precision numerical solution reproducing the classical and one-loop string predictions very accurately. We also analytically compute the first 7 nontrivial orders of the weak coupling expansion.
Heavy quarks and CP: Moriond 1985
Energy Technology Data Exchange (ETDEWEB)
Bjorken, J.D.
1985-03-01
The presentations at the Fifth Moriond Workshop on Heavy Quarks, Flavor Mixing, and CP Violation (La Plagne, France, January 13-19, 1985) are summarized. The following topics are reviewed. What's New (beyond the top, top quarks, bottom quarks, charm quarks, strange quarks, and others); why is all this being done (strong interactions and hadron structure, and electroweak properties); and what next (facilities and can one see CP violation in the B-anti B system). 64 refs., 10 figs.
Structure of Nonlocal Vacuum Condensate of Quarks
Institute of Scientific and Technical Information of China (English)
周丽娟; 马维兴
2003-01-01
The Dyson-Schwinger formalism is used to derive a fully dressed quark propagator. By use of the derived form of the quark propagator, the structure of non-local quark vacuum condensate is studied, and the values of local quark vacuum condensate as well as quark gluon mixed condensate are calculated. The theoretical predictions are in good agreement with the empirical one used commonly in the literature.
Covariant Formulations of Superstring Theories.
Mikovic, Aleksandar Radomir
1990-01-01
Chapter 1 contains a brief introduction to the subject of string theory, and tries to motivate the study of superstrings and covariant formulations. Chapter 2 describes the Green-Schwarz formulation of the superstrings. The Hamiltonian and BRST structure of the theory is analysed in the case of the superparticle. Implications for the superstring case are discussed. Chapter 3 describes the Siegel's formulation of the superstring, which contains only the first class constraints. It is shown that the physical spectrum coincides with that of the Green-Schwarz formulation. In chapter 4 we analyse the BRST structure of the Siegel's formulation. We show that the BRST charge has the wrong cohomology, and propose a modification, called first ilk, which gives the right cohomology. We also propose another superparticle model, called second ilk, which has infinitely many coordinates and constraints. We construct the complete BRST charge for it, and show that it gives the correct cohomology. In chapter 5 we analyse the properties of the covariant vertex operators and the corresponding S-matrix elements by using the Siegel's formulation. We conclude that the knowledge of the ghosts is necessary, even at the tree level, in order to obtain the correct S-matrix. In chapter 6 we attempt to calculate the superstring loops, in a covariant gauge. We calculate the vacuum-to -vacuum amplitude, which is also the cosmological constant. We show that it vanishes to all loop orders, under the assumption that the free covariant gauge-fixed action exists. In chapter 7 we present our conclusions, and briefly discuss the random lattice approach to the string theory, as a possible way of resolving the problem of the covariant quantization and the nonperturbative definition of the superstrings.
Dumé, Belle
2003-01-01
"Physicists working at the Relativistic Heavy Ion Collider (RHIC) at the Brookhaven National Laboratory in the US say that they have come closer than ever before to creating a quark-gluon plasma" (0.5 page)
Quark Model and multiquark system
da Silva, Cristiane Oldoni
2010-01-01
The discovery of many particles, especially in the 50's, when the firsts accelerators appeared, caused the searching for a model that would describe in a simple form the whole of known particles. The Quark Model, based in the mathematical structures of group theory, provided in the beginning of the 60's a simplified description of hadronic matter already known, proposing that three particles, called quarks, would originate all the observed hadrons. This model was able to preview the existence of particles that were later detected, confirming its consistency. Extensions of the Quark Model were made in the beginning of the 70's, focusing in describing observed particles that were excited states of the fundamental particles and others that presented new quantum numbers (flavors). Recently, exotic states as tetraquarks and pentaquarks types, also called multiquarks systems, previewed by the model, were observed, what renewed the interest in the way as quarks are confined inside the hadrons. In this article we pre...
Abachi, S.; Abbott, B.; Abolins, M.; Acharya, B. S.; Adam, I.; Adams, D. L.; Adams, M.; Ahn, S.; Aihara, H.; Alitti, J.; Álvarez, G.; Alves, G. A.; Amidi, E.; Amos, N.; Anderson, E. W.; Aronson, S. H.; Astur, R.; Avery, R. E.; Baden, A.; Balamurali, V.; Balderston, J.; Baldin, B.; Bantly, J.; Bartlett, J. F.; Bazizi, K.; Bendich, J.; Beri, S. B.; Bertram, I.; Bezzubov, V. A.; Bhat, P. C.; Bhatnagar, V.; Bhattacharjee, M.; Bischoff, A.; Biswas, N.; Blazey, G.; Blessing, S.; Boehnlein, A.; Bojko, N. I.; Borcherding, F.; Borders, J.; Boswell, C.; Brandt, A.; Brock, R.; Bross, A.; Buchholz, D.; Burtovoi, V. S.; Butler, J. M.; Casey, D.; Castilla-Valdez, H.; Chakraborty, D.; Chang, S.-M.; Chekulaev, S. V.; Chen, L.-P.; Chen, W.; Chevalier, L.; Chopra, S.; Choudhary, B. C.; Christenson, J. H.; Chung, M.; Claes, D.; Clark, A. R.; Cobau, W. G.; Cochran, J.; Cooper, W. E.; Cretsinger, C.; Cullen-Vidal, D.; Cummings, M.; Cutts, D.; Dahl, O. I.; de, K.; Demarteau, M.; Demina, R.; Denisenko, K.; Denisenko, N.; Denisov, D.; Denisov, S. P.; Dharmaratna, W.; Diehl, H. T.; Diesburg, M.; di Loreto, G.; Dixon, R.; Draper, P.; Drinkard, J.; Ducros, Y.; Dugad, S. R.; Durston-Johnson, S.; Edmunds, D.; Efimov, A. O.; Ellison, J.; Elvira, V. D.; Engelmann, R.; Eno, S.; Eppley, G.; Ermolov, P.; Eroshin, O. V.; Evdokimov, V. N.; Fahey, S.; Fahland, T.; Fatyga, M.; Fatyga, M. K.; Featherly, J.; Feher, S.; Fein, D.; Ferbel, T.; Finocchiaro, G.; Fisk, H. E.; Fisyak, Yu.; Flattum, E.; Forden, G. E.; Fortner, M.; Frame, K. C.; Franzini, P.; Fredriksen, S.; Fuess, S.; Galjaev, A. N.; Gallas, E.; Gao, C. S.; Gao, S.; Geld, T. L.; Genik, R. J., II; Genser, K.; Gerber, C. E.; Gibbard, B.; Glaubman, M.; Glebov, V.; Glenn, S.; Glicenstein, J. F.; Gobbi, B.; Goforth, M.; Goldschmidt, A.; Gomez, B.; Goncharov, P. I.; Gordon, H.; Goss, L. T.; Graf, N.; Grannis, P. D.; Green, D. R.; Green, J.; Greenlee, H.; Griffin, G.; Grossman, N.; Grudberg, P.; Grünendahl, S.; Guida, J. A.; Guida, J. M.; Guryn, W.; Gurzhiev, S. N.; Gutnikov, Y. E.; Hadley, N. J.; Haggerty, H.; Hagopian, S.; Hagopian, V.; Hahn, K. S.; Hall, R. E.; Hansen, S.; Hatcher, R.; Hauptman, J. M.; Hedin, D.; Heinson, A. P.; Heintz, U.; Hernandez-Montoya, R.; Heuring, T.; Hirosky, R.; Hobbs, J. D.; Hoeneisen, B.; Hoftun, J. S.; Hsieh, F.; Hu, Ting; Hu, Tong; Huehn, T.; Igarashi, S.; Ito, A. S.; James, E.; Jaques, J.; Jerger, S. A.; Jiang, J. Z.-Y.; Joffe-Minor, T.; Johari, H.; Johns, K.; Johnson, M.; Johnstad, H.; Jonckheere, A.; Jöstlein, H.; Jun, S. Y.; Jung, C. K.; Kahn, S.; Kang, J. S.; Kehoe, R.; Kelly, M.; Kernan, A.; Kerth, L.; Kim, C. L.; Kim, S. K.; Klatchko, A.; Klima, B.; Klochkov, B. I.; Klopfenstein, C.; Klyukhin, V. I.; Kochetkov, V. I.; Kohli, J. M.; Koltick, D.; Kostritskiy, A. V.; Kotcher, J.; Kourlas, J.; Kozelov, A. V.; Kozlovski, E. A.; Krishnaswamy, M. R.; Krzywdzinski, S.; Kunori, S.; Lami, S.; Landsberg, G.; Lanou, R. E.; Lebrat, J.-F.; Lee-Franzini, J.; Leflat, A.; Li, H.; Li, J.; Li, Y. K.; Li-Demarteau, Q. Z.; Lima, J. G.; Lincoln, D.; Linn, S. L.; Linnemann, J.; Lipton, R.; Liu, Y. C.; Lobkowicz, F.; Loken, S. C.; Lökös, S.; Lueking, L.; Lyon, A. L.; Maciel, A. K.; Madaras, R. J.; Madden, R.; Mandrichenko, I. V.; Mangeot, Ph.; Mani, S.; Mansoulié, B.; Mao, H. S.; Margulies, S.; Markeloff, R.; Markosky, L.; Marshall, T.; Martin, M. I.; Marx, M.; May, B.; Mayorov, A. A.; McCarthy, R.; McKibben, T.; McKinley, J.; Melanson, H. L.; de Mello Neto, J. R.; Merritt, K. W.; Miettinen, H.; Milder, A.; Milner, C.; Mincer, A.; de Miranda, J. M.; Mishra, C. S.; Mohammadi-Baarmand, M.; Mokhov, N.; Mondal, N. K.; Montgomery, H. E.; Mooney, P.; Mudan, M.; Murphy, C.; Murphy, C. T.; Nang, F.; Narain, M.; Narasimham, V. S.; Narayanan, A.; Neal, H. A.; Negret, J. P.; Neis, E.; Nemethy, P.; NešiĆ, D.; Norman, D.; Oesch, L.; Oguri, V.; Oltman, E.; Oshima, N.; Owen, D.; Padley, P.; Pang, M.; Para, A.; Park, C. H.; Park, Y. M.; Partridge, R.; Parua, N.; Paterno, M.; Perkins, J.; Peryshkin, A.; Peters, M.; Piekarz, H.; Pischalnikov, Y.; Pluquet, A.; Podstavkov, V. M.; Pope, B. G.; Prosper, H. B.; Protopopescu, S.; Pušeljić, D.; Qian, J.; Quintas, P. Z.; Raja, R.; Rajagopalan, S.; Ramirez, O.; Rao, M. V.; Rapidis, P. A.; Rasmussen, L.; Read, A. L.; Reucroft, S.; Rijssenbeek, M.; Rockwell, T.; Roe, N. A.; Roldan, J. M.; Rubinov, P.; Ruchti, R.; Rusin, S.; Rutherfoord, J.; Santoro, A.; Sawyer, L.; Schamberger, R. D.; Schellman, H.; Schmid, D.; Sculli, J.; Shabalina, E.; Shaffer, C.; Shankar, H. C.; Shivpuri, R. K.; Shupe, M.; Singh, J. B.; Sirotenko, V.; Smart, W.; Smith, A.; Smith, R. P.; Snihur, R.; Snow, G. R.; Snyder, S.; Solomon, J.; Sood, P. M.; Sosebee, M.; Souza, M.; Spadafora, A. L.; Stephens, R. W.; Stevenson, M. L.; Stewart, D.; Stocker, F.; Stoianova, D. A.; Stoker, D.; Streets, K.; Strovink, M.; Taketani, A.; Tamburello, P.; Tarazi, J.; Tartaglia, M.; Taylor, T. L.; Teiger, J.; Thompson, J.; Trippe, T. G.; Tuts, P. M.; Varelas, N.; Varnes, E. W.; Virador, P. R.; Vititoe, D.; Volkov, A. A.; von Goeler, E.; Vorobiev, A. P.; Wahl, H. D.; Wang, J.; Wang, L. Z.; Warchol, J.; Wayne, M.; Weerts, H.; Wenzel, W. A.; White, A.; White, J. T.; Wightman, J. A.; Wilcox, J.; Willis, S.; Wimpenny, S. J.; Wirjawan, J. V.; Wolf, Z.; Womersley, J.; Won, E.; Wood, D. R.; Xu, H.; Yamada, R.; Yamin, P.; Yanagisawa, C.; Yang, J.; Yasuda, T.; Yoshikawa, C.; Youssef, S.; Yu, J.; Yu, Y.; Zhang, Y.; Zhou, Y. H.; Zhu, Q.; Zhu, Y. S.; Zhu, Z. H.; Zieminska, D.; Zieminski, A.; Zinchenko, A.; Zylberstejn, A.
1995-04-01
The D0 Collaboration reports on a search for the standard model top quark in pp¯ collisions at s = 1.8 TeV at the Fermilab Tevatron with an integrated luminosity of approximately 50 pb-1. We have searched for tt¯ production in the dilepton and single-lepton decay channels with and without tagging of b-quark jets. We observed 17 events with an expected background of 3.8+/-0.6 events. The probability for an upward fluctuation of the background to produce the observed signal is 2×10-6 (equivalent to 4.6 standard deviations). The kinematic properties of the excess events are consistent with top quark decay. We conclude that we have observed the top quark and measured its mass to be 199+19-21 (stat) +/-22 (syst) GeV/c2 and its production cross section to be 6.4+/-2.2 pb.
Solid Bare Strange Quark Stars
Xu, R X
2003-01-01
The reason, we need three terms of `strange', `bare', and `solid' before quark stars, is presented concisely though some fundamental issues are not certain. Observations favoring these stars are introduced.
Semileptonic Decays of Heavy Lambda Baryons in a Quark Model
Energy Technology Data Exchange (ETDEWEB)
Winston Roberts; Muslema Pervin; Simon Capstick
2005-03-01
The semileptonic decays of {Lambda}{sub c} and {Lambda}{sub b} are treated in the framework of a constituent quark model. Both nonrelativistic and semirelativistic Hamiltonians are used to obtain the baryon wave functions from a fit to the spectra, and the wave functions are expanded in both the harmonic oscillator and Sturmian bases. The latter basis leads to form factors in which the kinematic dependence on q{sup 2} is in the form of multipoles, and the resulting form factors fall faster as a function of q{sup 2} in the available kinematic ranges. As a result, decay rates obtained in the two models using the Sturmian basis are significantly smaller than those obtained using the harmonic oscillator basis. In the case of the {Lambda}{sub c}, decay rates calculated using the Sturmian basis are closer to the experimentally reported rates. However, we find a semileptonic branching fraction for the {Lambda}{sub c} to decay to excited {Lambda}* states of 11% to 19%, in contradiction with what is assumed in available experimental analyses. Our prediction for the {Lambda}{sub b} semileptonic decays is that decays to the ground state {Lambda}{sub c} provide a little less than 70% of the total semileptonic decay rate. For the decays {Lambda}{sub b} {yields} {Lambda}{sub c}, the analytic form factors we obtain satisfy the relations expected from heavy-quark effective theory at the non-recoil point, at leading and next-to-leading orders in the heavy-quark expansion. In addition, some features of the heavy-quark limit are shown to naturally persist as the mass of the heavy quark in the daughter baryon is decreased.
Top Quark Physics: Future Measurements
Energy Technology Data Exchange (ETDEWEB)
Jaros, John A
2003-05-09
We discuss the study of the top quark at future experiments and machines. Top's large mass makes it a unique probe of physics at the natural electroweak scale. We emphasize measurements of the top quark's mass, width, and couplings, as well as searches for rare or nonstandard decays, and discuss the complementary roles played by hadron and lepton colliders.
Stability of Quark Star Models
Azam, M.; Mardan, S. A.; Rehman, M. A.
2016-05-01
In this paper, we investigate the stability of quark stars with four different types of inner matter configurations; isotropic, charged isotropic, anisotropic and charged anisotropic by using the concept of cracking. For this purpose, we have applied local density perturbations technique to the hydrostatic equilibrium equation as well as on physical parameters involved in the model. We conclude that quark stars become potentially unstable when inner matter configuration is changed and electromagnetic field is applied.
Pourquoi les quarks restent invisibles
Gross, David J
2005-01-01
At the beginning of the seventies, physicists discovered a new scale in the matter structure. Protons and neutrons, components of the atomic nucleus, seemed to be constituted by even more elementar particles: the quarks. But while they seemed to move freely inside the protons, it was impossible to isolate one of these quarks. The Nobel Prize for physics rewarded the explanation of this phenomenon (3 pages)
Heavy quark production and spectroscopy
Energy Technology Data Exchange (ETDEWEB)
Appel, J.A.
1993-11-01
This review covers many new experimental results on heavy flavor production and spectroscopy. It also shows some of the increasingly improved theoretical understanding of results in light of basic perturbative QCD and heavy quark symmetry. At the same time, there are some remaining discrepancies among experiments as well as significant missing information on some of the anticipated lowest lying heavy quark states. Most interesting, perhaps, are some clearly measured production effects awaiting full explanation.
The strange-quark distribution
Energy Technology Data Exchange (ETDEWEB)
Barone, V. [Turin Univ. (Italy). Ist. di Fisica Teorica; Genovese, M. [Turin Univ. (Italy). Ist. di Fisica Teorica]|[European Organization for Nuclear Research, Geneva (Switzerland). Theory Div.; Nikolaev, N.N. [Forschungszentrum Juelich GmbH (Germany). Inst. fuer Kernphysik]|[L.D. Landau Institute for Theoretical Physics, Moscow (Russian Federation); Predazzi, E. [Turin Univ. (Italy). Ist. di Fisica Teorica; Zakharov, B.G. [L.D. Landau Institute for Theoretical Physics, Moscow (Russian Federation)
1996-03-01
We discuss the latest CCFR determination of the strange sea density of the proton. We comment on the differences with a previous, leading-order, result and point out the relevance of quark mass effects and current non-conservation effects. By taking them into account it is possible to solve the residual discrepancy with another determination of the strange-quark distribution. Two important sources of uncertainties are also analysed. (orig.). With 4 figs.
Deconfinement and virtual quark loops
Çelik, T.; Engels, J.; Satz, H.
1983-12-01
We calculate paer Monte Carlo evaluation on an 83 × 3 lattice the energy density ɛG of the gluon sector of QCD, including virtual quark loops up to the fourth power in the hopping parameter expansion. For light quarks of one flavour, we observe at T/ΛL 95 +/- 10 a rapid variation of ɛG in T, accompanied by strong fluctuations from iteration to iteration. as clear signal of the deconfinement transition.
Study of the $ar{D}$N Interaction in a QCD Coulomb Gauge Quark Model
Directory of Open Access Journals (Sweden)
Vizcarra V.E.
2010-04-01
Full Text Available We study the $ar{D}$N interaction at low energies with a quark model inspired in the QCD Hamiltonian in Coulomb gauge. The model Hamiltonian incorporates a conﬁning Coulomb potential extracted from a self-consistent quasiparticle method for the gluon degrees of freedom, and transverse-gluon hyperﬁne interaction consistent with a ﬁnite gluon propagator in the infrared. Initially a constituent-quark mass function is obtained by solving a gap equation and baryon and meson bound-states are obtained in Fock space using a variational calculation. Next, having obtained the constituent-quark masses and the hadron waves functions, an eﬀective meson-nucleon interaction is derived from a quark-interchange mechanism. This leads to a short range mesonbaryon interaction and to describe long-distance physics vector- and scalar-meson exchanges described by eﬀective Lagrangians are incorporated. The derived eﬀective $ar{D}$N potential is used in a Lippmann-Schwinger equation to obtain phase shifts. The results are compared with a recent similar calculation using the nonrelativistic quark model.
Unquenched QCD with Light Quarks
Duncan, A; Yoo, J
2003-01-01
We present recent results in unquenched lattice QCD with two degenerate light sea quarks using the truncated determinant approximation (TDA). In the TDA the infrared modes contributing to the quark determinant are computed exactly up to some cutoff in quark off-shellness (typically 2$\\Lambda_{QCD}$). This approach allows simulations to be performed at much lighter quark masses than possible with conventional hybrid MonteCarlo techniques. Results for the static energy and topological charge distributions are presented using a large ensemble generated on very coarse (6$^4$) but physically large lattices. Preliminary results are also reported for the static energy and meson spectrum on 10$^3$x20 lattices (lattice scale $a^{-1}$=1.15 GeV) at quark masses corresponding to pions of mass $\\leq$ 200 MeV. Using multiboson simulation to compute the ultraviolet part of the quark determinant the TDA approach becomes an exact with essentially no increase in computational effort. Some preliminary results using this fully u...
Polarization in heavy quark decays
Energy Technology Data Exchange (ETDEWEB)
Alimujiang, K.
2006-07-01
In this thesis I concentrate on the angular correlations in top quark decays and their next.to.leading order (NLO) QCD corrections. I also discuss the leading.order (LO) angular correlations in unpolarized and polarized hyperon decays. In the first part of the thesis I calculate the angular correlation between the top quark spin and the momentum of decay products in the rest frame decay of a polarized top quark into a charged Higgs boson and a bottom quark in Two-Higgs-Doublet-Models: t({up_arrow}) {yields} b + H{sup +}. I provide closed form formulae for the O({alpha}{sub s}) radiative corrections to the unpolarized and the polar correlation functions for m{sub b}{ne}0 and m{sub b}=0. In the second part I concentrate on the semileptonic rest frame decay of a polarized top quark into a bottom quark and a lepton pair: t({up_arrow}){yields}X{sub b}+l{sup +}+{nu}{sub l}. I present closed form expressions for the O({alpha}{sub s}) radiative corrections to the unpolarized part and the polar and azimuthal correlations for m{sub b}{ne}0 and m{sub b}=0. In the last part I turn to the angular distribution in semileptonic hyperon decays. Using the helicity method I derive complete formulas for the leading order joint angular decay distributions occurring in semileptonic hyperon decays including lepton mass and polarization effects. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Jung, A. W. [Fermilab
2014-09-24
Recent measurements of top-quark properties at the LHC and the Tevatron are presented. Most recent measurements of the top quark mass have been carried out by CMS using $19.7/$fb of $\\sqrt{s} = 8$ TeV data including the study of the dependence on event kinematics. ATLAS uses the full Run I data at $\\sqrt{s} = 7$ TeV for a "3D" measurement that significantly reduces systematic uncertainties. D0 employs the full Run II data using the matrix element method to measure the top quark mass with significantly reduced systematic uncertainties. Many different measurements of the top quark exist to date and the most precise ones per decay channel per experiment have been combined into the first world combination with a relative precision of 0.44%. Latest updates of measurements of production asymmetries include the measurement of the \\ttbar production asymmetry by D0 employing the full Run II data set, by CMS and ATLAS (including the polarization of the top quark) employing both the full data set at $\\sqrt{s} = 7$ TeV. CMS uses the full $\\sqrt{s} = 8$ TeV data to measure the top quark polarization in single top production, the ratio ${\\cal R}$ of the branching fractions ${\\cal B}(t \\rightarrow Wb) / {\\cal B}(t \\rightarrow Wq)$ and to search for flavor changing neutral currents. The results from all these measurements agree well with their respective Standard Model expectation.
Baryon spectrum analysis using Dirac's covariant constraint dynamics
Whitney, Joshua F.; Crater, Horace W.
2014-01-01
We present a relativistic quark model for the baryons that combines three related relativistic formalisms. The three-body constraint formalism of Sazdjian is used to recast three relativistic two-body equations for the three pairs of interacting quarks into a single relativistically covariant three-body equation for the bound state energies, having a Schrodinger-like structure. The two-body equations are the two-body Dirac equations of constraint dynamics derived by Crater and Van Alstine for combined world vector and scalar interactions providing the necessary spin dependent and spin independent interaction terms. The minimal quasipotential formalism of Todorov is used to provide an invariant framework for the vector and scalar dynamics used in the two-body Dirac equations into which is inserted a local simplified version of the Richardson potential. The spectral results are analyzed and compared to experiment using a best fit method and several different algorithms, including a gradient approach, and a Monte Carlo method.
Energy Technology Data Exchange (ETDEWEB)
Barik, N.; Das, M.
1983-12-01
The effect of confinement on the magnetic moment of a quark has been studied in a simple independent-quark model based on the Dirac equation with a power-law potential. The magnetic moments so obtained for the constituent quarks, which are found to be significantly different from their corresponding Dirac moments, are used in predicting the magnetic moments of baryons in the nucleon octet as well as those in the charmed and b-flavored sectors. We not only get an improved result for the proton magnetic moment, but the calculation for the rest of the nucleon octet also turns out to be in reasonable agreement with experiment. The overall predictions for the charmed and b-flavored baryons are also comparable with other model predictions.
Measurement of top quark properties at CMS
Piedra Gomez, Jonatan
2015-01-01
Measurements of top quark properties in top quark decays are presented, using data collected by the CMS experiment during the years 2011 and 2012. The polarization of W bosons in top quark decays is measured. The W boson helicity fractions and angular asymmetries are extracted, and limits on anomalous contributions to the Wtb vertex are determined. Furthermore, searches for flavor changing neutral currents in top quark decays are presented. The flavor contents in top quark pair events are measured using the fraction of top quarks decaying into a W boson and a b quark relative to all top quark decays, $R=BR({\\rm t} \\to {\\rm Wb})/BR({\\rm t} \\to {\\rm Wq})$, and the result is used to determine the CKM matrix element $V_{\\rm tb}$ as well as the width of the top quark resonance.
Discrete Symmetries in Covariant LQG
Rovelli, Carlo
2012-01-01
We study time-reversal and parity ---on the physical manifold and in internal space--- in covariant loop gravity. We consider a minor modification of the Holst action which makes it transform coherently under such transformations. The classical theory is not affected but the quantum theory is slightly different. In particular, the simplicity constraints are slightly modified and this restricts orientation flips in a spinfoam to occur only across degenerate regions, thus reducing the sources of potential divergences.
Höing, Rebekka Sophie; Haller, Johannes
2015-01-01
A search for pairs of vector-like T' quark produced in proton-proton collisions recorded with the CMS experiment at p s = 8 TeV is presented. The search is optimized for decays of T' quarks to top quarks and Higgs bosons, where the top quarks and Higgs bosons decay hadronically. The T'-quark mass range between 500 and 1000 GeV is investigated. The top quarks and Higgs bosons produced in decays of the heavy T' quarks acquire large Lorentz boosts. The signatures of these particles in the detector can overlap and are therefore dicult to resolve using classical jet reconstruction methods. Large-radius jets are reconstructed and subjets formed from their constituents. The decay products of particles with large Lorentz boosts are highly collimated and can all be found within a single one of these large-radius jets. Top jets containing hadronic top-quark decays are identied with a top-tagging algorithm that analyzes the jet substructure. A b-tagging algorithm is applied to the reconstructed subjets in order to nd bo...
Phenotypic covariance at species’ borders
2013-01-01
Background Understanding the evolution of species limits is important in ecology, evolution, and conservation biology. Despite its likely importance in the evolution of these limits, little is known about phenotypic covariance in geographically marginal populations, and the degree to which it constrains, or facilitates, responses to selection. We investigated phenotypic covariance in morphological traits at species’ borders by comparing phenotypic covariance matrices (P), including the degree of shared structure, the distribution of strengths of pair-wise correlations between traits, the degree of morphological integration of traits, and the ranks of matricies, between central and marginal populations of three species-pairs of coral reef fishes. Results Greater structural differences in P were observed between populations close to range margins and conspecific populations toward range centres, than between pairs of conspecific populations that were both more centrally located within their ranges. Approximately 80% of all pair-wise trait correlations within populations were greater in the north, but these differences were unrelated to the position of the sampled population with respect to the geographic range of the species. Conclusions Neither the degree of morphological integration, nor ranks of P, indicated greater evolutionary constraint at range edges. Characteristics of P observed here provide no support for constraint contributing to the formation of these species’ borders, but may instead reflect structural change in P caused by selection or drift, and their potential to evolve in the future. PMID:23714580
Institute of Scientific and Technical Information of China (English)
DONG Yu-Bing; FENG Qing-Guo
2002-01-01
Based on a relativistic quark model approach, the transition properties of the first nucleon resonance △(1232), and the coupling constants gπNN, g△πN are investigated. Tvo different vays to remove the center of mass motion are considered. The results of the relativistic approaches with and without center ofmass correction are compared with those of nonrelativistic constituent quark model. Moreover, pion meson cloud effect on these calculated observables is explicitly addressed. Better results are obtained by taking the pion meson cloud into account.
Determination of Deuteron Dipole Moment in Nuclear Quark-Like Model
Institute of Scientific and Technical Information of China (English)
N.Ghahramany; E.Yazdankish
2013-01-01
Using the quark-like model,we have improved the existing deviation between theoretical and experimental values of magnetic dipole moment of deuteron.Based upon Pauli Exclusion Principle,the constituent quarks form a ground state for l =0.The expectation value of the deuteron magnetic dipole moment operator is determined to be equal to 0.861 5978μN in better agreement with the measured value of 0.8574376μN as compared to the shell model calculations.
AUTHOR|(SzGeCERN)655637
The measurement of prompt photon associated with a b jet in proton-proton interactions can provide us insight into the inner structure of proton. This is because precision of determination of parton distribution functions of b quark and gluon can be increased by such a measurement. The measurement of cross-section of prompt photon associated with a b jet (process $pp\\longrightarrow \\gamma + b + X$) at $\\sqrt{s}$= 8 TeV with the ATLAS detector is presented. Full 8 TeV dataset collected by ATLAS during the year 2012 was used in this analysis. Corresponding integrated luminosity is 20.3 $fb^{-1}$. Fiducial differential cross-section as a function of photon transverse momentum at particle level was extracted from data and compared with the prediction of leading order event generator Pythia 8. Cross-section extracted from data is normalised independently on the Monte Carlo prediction. Values of data distribution lie above Monte Carlo values. The difference can be explained by presence of higher order effects not ...
Quasiparticle properties of the quarks of the Nambu--Jona-Lasinio model
Energy Technology Data Exchange (ETDEWEB)
Cao, N.; Shakin, C.M.; Sun, W. (Department of Physics and Center for Nuclear Theory, Brooklyn College of the City University of New York, Brooklyn, New York 11210 (United States))
1992-12-01
In spite of the apparent limitations of the model, in recent years there have been many applications of the Nambu--Jona-Lasinio (NJL) model in the study of hadron structure and in the study of the behavior of nuclear matter at finite temperature and density. A number of researchers have studied a generalized SU(3) version of the NJL model. For example, Vogl, Lutz, Klimt, and Weise (Nucl. Phys. A516 469 (1990)) have performed extensive calculations that include a calculation of a scalar form factor of a constituent quark, {ital F}{sub {ital s}}({ital q}{sup 2}), and a calculation of a quark sigma term {sigma}{sub {ital q}}. (In their work, the latter quantity is related to the nucleon sigma term {sigma}{sub {ital N}} as in a constituent quark model: {sigma}{sub {ital N}}=3{sigma}{sub {ital q}}.) These calculations are made in what may be termed a sigma-dominance approximation. In the work reported here, we review the important role played by the nucleon sigma term in understanding the behavior of the quark condensate in the presence of matter. We make use of the original SU(2) version of the NJL model to study how various quark properties are modified when we take into account the dressing of the constituent quarks by the pion, the Goldstone boson of the model. We calculate the quark self-energy arising from emission and absorption of a pion and also show how the calculation of the scalar form factor of the quark and {sigma}{sub {ital q}} are modified due to the coupling of the quark to the pion. The correction terms considered here serve to reduce the value of {sigma}{sub {ital q}} by a small amount relative to the value obtained in the simplest version of the sigma dominance model. For example, for a Euclidean momentum cutoff, {Lambda}=1050 MeV, the uncorrected result is {sigma}{sub {ital N}}=54.6 MeV.
Strange Quark Matter Status and Prospects
Sandweiss, J.
2004-01-01
The existence of quark states with more than three quarks is allowed in QCD. The stability of such quark matter states has been studied with lattice QCD and phenomenological bag models, but is not well constrained by theory. The addition of strange quarks to the system allows the quarks to be in lower energy states despite the additional mass penalty. There is additional stability from reduced Coulomb repulsion. SQM is expected to have a low Z/A. Stable or metastable massive multiquark states contain u, d, and s quarks.
Selected top quark mass measurements at CMS
Bouvier, Elvire
2016-01-01
Selected measurements of the top quark mass are presented, obtained from CMS data collected in proton-proton collisions at the LHC at center-of-mass energies of 7, 8, and 13 TeV. ``Standard'' techniques are employed in each decay channel of top quark pair events and their results are combined. The mass of the top quark is also measured using several ``alternative'' methods, including measurements from shapes of top quark decay distributions in single top quark and top quark pair events as well as pole mass measurements.
Propagators and Masses of Light Quarks
Institute of Scientific and Technical Information of China (English)
ZHOU Li-Juan; ZHU Ji-Zhen; MA Wei-Xing
2003-01-01
Based on Dyson-Schwinger equations in "rainbow" approximation, fully dressed confining quark propagator is obtained, and then the masses of light quarks (mu, md, and ms) are derived from the fully dressed confining quark propagator. At the same time, the local and non-local quark vacuum condensates as well as the quark-gluon mixed condensate are also predicted. Furthermore, the quark masses are also deduced from the Gell-Mann-Oakes-Renner relation and chiral perturbative theory. The results from different methods are consistent with each other.
Propagators and Masses of Light Quarks
Institute of Scientific and Technical Information of China (English)
ZHOULi-Juan; ZHUJi-Zhen; MAWei-Xing
2003-01-01
Based on Dyson-Schwinger equations in “rainbow” approximation, fully dressed confining quark propagator is obtained, and then the masses of light quarks (mu, md, and ms) are derived from the fully dressed confining quark propagator. At the same time, the local and non-local quark vacuum condensates as well as the quark-gluon mixed condensate are also predicted. Furthermore, the quark masses are also deduced from the Gell-Mann-Oakes-Renner relation and chiral perturbative theory. The results from different methods are consistent with each other.
Influence of the nonperturbative quark-gluon vertex on the meson and baryon spectrum
Energy Technology Data Exchange (ETDEWEB)
Williams, Richard; Sanchis-Alepuz, Hèlios [Institut für Theoretische Physik, Justus-Liebig–Universität Giessen, 35392 Giessen (Germany)
2016-01-22
We present a calculation of the Hadron spectrum in the Dyson-Schwinger/Bethe-Salpeter approach to continuum QCD. A sophisticated truncation featuring all covariant structures of the quark-gluon vertex, with its inherent flavour dependence, is employed in a framework that preserves the dynamics of chiral symmetry breaking. The study is suggestive as to the relevance of additional resonant and non-resonant two- and three-body contributions.
Competing risks and time-dependent covariates
DEFF Research Database (Denmark)
Cortese, Giuliana; Andersen, Per K
2010-01-01
Time-dependent covariates are frequently encountered in regression analysis for event history data and competing risks. They are often essential predictors, which cannot be substituted by time-fixed covariates. This study briefly recalls the different types of time-dependent covariates...
The QCD string with quarks; 1, spinless quarks
Dubin, A Yu; Simonov, Yu A
1993-01-01
Starting from the QCD Lagrangian we derive the effective action for massive quark and antiquark at large distances, corresponding to the minimal area low of the Wilson loop. The path integral method is used to quantize the system and the spectrum is obtained with asymptotically linear Regge trajectories. Two dynamical regimes distinguished by the string energy--momentum distribution are found: at large orbital excitations ($l\\gg 1$) the system behaves as a string and yields the Regge slope of $\\frac{1}{2 \\pi \\sigma}$, while at small $l$ one obtains a potential-like regime for relativistic or nonrelativistic system . The problem of relative time is clarified. It is shown that in the valence quark approximation one can reduce the initial four-dimensional dynamics to the three-dimensional one. The limiting case of a pure string (without quark kinetic terms) is studied and the spectrum of the straight-line string is obtained.
Constituents of Doubly Periodic Instantons
Ford, C; Ford, Chris; Pawlowski, Jan M.
2002-01-01
Using the Nahm transform we investigate doubly periodic charge one SU(2) instantons with radial symmetry. Two special points where the Nahm zero modes have softer singularities are identified as constituent locations. To support this picture, the action density is computed analytically and numerically within a two dimensional slice containing the two constituents. For particular values of the parameters the torus can be cut in half yielding two copies of a twisted charge 1/2 instanton. Such objects comprise a single constituent.
Duality between quark-quark and quark-antiquark pairing in 1+1 dimensional large N models
Thies, M
2003-01-01
We identify a canonical transformation which maps the chiral Gross-Neveu model onto a recently proposed Cooper pair model. Baryon number and axial charge are interchanged. The same physics can be described either as chiral symmetry breaking (quark-antiquark pairing) or as superconductivity (quark-quark pairing).
Covariance Evaluation Methodology for Neutron Cross Sections
Energy Technology Data Exchange (ETDEWEB)
Herman,M.; Arcilla, R.; Mattoon, C.M.; Mughabghab, S.F.; Oblozinsky, P.; Pigni, M.; Pritychenko, b.; Songzoni, A.A.
2008-09-01
We present the NNDC-BNL methodology for estimating neutron cross section covariances in thermal, resolved resonance, unresolved resonance and fast neutron regions. The three key elements of the methodology are Atlas of Neutron Resonances, nuclear reaction code EMPIRE, and the Bayesian code implementing Kalman filter concept. The covariance data processing, visualization and distribution capabilities are integral components of the NNDC methodology. We illustrate its application on examples including relatively detailed evaluation of covariances for two individual nuclei and massive production of simple covariance estimates for 307 materials. Certain peculiarities regarding evaluation of covariances for resolved resonances and the consistency between resonance parameter uncertainties and thermal cross section uncertainties are also discussed.
Explicit and Dynamical Chiral Symmetry Bresking in an Effective Quark-Quark Interaction Model
Institute of Scientific and Technical Information of China (English)
宗红石; 吴小华; 侯丰尧; 赵恩广
2004-01-01
A method for obtaining the small current quark mass effect on the dressed quark propagator from an effective quark-quark interaction model is developed. Within this approach both the explicit and dynamical chiral symmetry breakings are analysed. A comparison with the previous results is given.
Lorcé, Cédric
2014-01-01
The proton spin puzzle issue focused the attention on the parton spin and orbital angular momentum contributions to the proton spin. However, a complete characterization of the proton spin structure requires also the knowledge of the parton spin-orbit correlation. We showed that this quantity can be expressed in terms of moments of measurable parton distributions. Using the available phenomenological information about the valence quarks, we concluded that this correlation is negative, meaning that the valence quark spin and kinetic orbital angular momentum are, in average, opposite. The quark spin-orbit correlation can also be expressed more intuitively in terms of relativistic phase-space distributions, which can be seen as the mother distributions of the standard generalized and transverse-momentum dependent parton distributions. We present here for the first time some examples of the general multipole decomposition of these phase-space distributions.
Gluon propagator with dynamical quarks
Papavassiliou, Joannis
2014-01-01
We review recent work on the effects of quark loops on the gluon propagator in the Landau gauge, relying mainly on the Schwinger-Dyson equations that describe the two-point sector of QCD. Particularly important in this context is the detailed study of how the standard gluon mass generation mechanism, which is responsible for the infrared finiteness of the quenched gluon propagator, is affected by the inclusions of dynamical quarks. This issue is especially relevant and timely, given the qualitative picture that emerges from recent unquenched lattice simulations. Our results demonstrate clearly that the gluon mass generation persists, and that the corresponding saturation points of the unquenched gluon propagators are progressively suppressed, as the number of quark flavors increases.
Energy Density in Quark-Gluon Plasma
Institute of Scientific and Technical Information of China (English)
马忠彪; 苗洪; 高崇寿
2003-01-01
We study the energy density in quark-gluon plasma. At the very high temperature, the quark matter is a hot and dense matter in the colour deconfinement condition, and quarks can coalescent diquarks. Energy density of this system is worked out and compared with the energy density in the other two kinds of situations. Possible energy density is about eo ≈ 2.4 GeV/fm3 according to our estimation for quark matter including diquarks,
Xu, J L
2002-01-01
We assume that the u quarks and the d quarks constitute a body center cubic quark lattice in the vacuum. Using energy band theory, we deduce an excited quark spectrum (from the quark lattice). Using the accompanying excitation concept, we deduce a baryon spectrum (including S, C, b, I, Q, and mass) from the quark spectrum. With a phenomenological binding energy formula, we deduce a meson spectrum (including S, C, b, I, Q, and mass) from the quark spectrum. The baryon and meson spectra agree well with experimental results. The BCC Quark Model predicts many new quarks (u'(3), d'(6)), baryons ($\\Lambda^0(4280)$, $\\Lambda_{C}^{+}(6600)$, $\\Lambda_{b}^{0}(9960))$, and mesons (K(3597), D(5996), B(9504), $\\eta(5926)$, $\\Upsilon(17805)$, T(1603) with I=2). The quarks u'(3) and d'(6) and the meson T(1603) have already been discovered.
Consistency between SU(3) and SU(2) covariant baryon chiral perturbation theory for the nucleon mass
Ren, Xiu-Lei; Alvarez-Ruso, L.; Geng, Li-Sheng; Ledwig, Tim; Meng, Jie; Vicente Vacas, M. J.
2017-03-01
Treating the strange quark mass as a heavy scale compared to the light quark mass, we perform a matching of the nucleon mass in the SU(3) sector to the two-flavor case in covariant baryon chiral perturbation theory. The validity of the 19 low-energy constants appearing in the octet baryon masses up to next-to-next-to-next-to-leading order [1] is supported by comparing the effective parameters (the combinations of the 19 couplings) with the corresponding low-energy constants in the SU(2) sector [2]. In addition, it is shown that the dependence of the effective parameters and the pion-nucleon sigma term on the strange quark mass is relatively weak around its physical value, thus providing support to the assumption made in Ref. [2] that the SU(2) baryon chiral perturbation theory can be applied to study nf = 2 + 1 lattice QCD simulations as long as the strange quark mass is close to its physical value.
Equilibration in quark gluon plasma
Das, S. K.; Alam, J.; Mohanty, P.
2011-07-01
The hydrodynamic expansion rate of quark gluon plasma (QGP) is evaluated and compared with the scattering rate of quarks and gluons within the system. Partonic scattering rates evaluated within the ambit of perturbative Quantum Choromodynamics (pQCD) are found to be smaller than the expansion rate evaluated with ideal equation of state (EoS) for the QGP. This indicate that during the space-time evolution the system remains out of equilibrium. Enhancement of pQCD cross sections and a more realistic EoS keep the partons closer to the equilibrium.
Equilibration in Quark Gluon Plasma
Das, Santosh K.; Alam, Jan-e; Mohanty, Payal
2009-01-01
The hydrodynamic expansion rate of quark gluon plasma (QGP) is evaluated and compared with the scattering rate of quarks and gluons within the system. Partonic scattering rates evaluated within the ambit of perturbative Quantum Choromodynamics (pQCD) are found to be smaller than the expansion rate evaluated with ideal equation of state (EoS) for the QGP. This indicate that during the space-time evolution the system remains out of equilibrium. Enhancement of pQCD cross sections and a more real...
Equilibration in Quark Gluon Plasma
Das, Santosh K; Mohanty, Payal
2009-01-01
The hydrodynamic expansion rate of quark gluon plasma (QGP) is evaluated and compared with the scattering rate of quarks and gluons within the system. Partonic scattering rates evaluated within the ambit of perturbative Quantum Choromodynamics (pQCD) are found to be smaller than the expansion rate evaluated with ideal equation of state (EoS) for the QGP. This indicate that during the space-time evolution the system remains out of equilibrium. Enhancement of pQCD cross sections and a more realistic EoS keep the partons closer to the equilibrium.
2016-01-01
This is the fifth volume in the series on the subject of quark-gluon plasma, a unique phase created in heavy-ion collisions at high energy. It contains review articles by the world experts on various aspects of quark-gluon plasma taking into account the advances driven by the latest experimental data collected at both the Relativistic Heavy-Ion Collider (RHIC) and the Large Hadron Collider (LHC). The articles are pedagogical and comprehensive which can be helpful for both new researchers entering the field as well as the experienced physicists working on the subject.
Searches for monopoles and quarks
Energy Technology Data Exchange (ETDEWEB)
Matis, H.S.
1986-07-01
Within the last year, several sensitive searches for monopoles and quarks have been done. Recent experiments at the Tevatron and at the CERN p anti p collider have detected no evidence for free fractional charge. An experiment in a iron refinery, which searched for GUT monopoles trapped in iron ore with two SQUID detectors, found no monopole candidate. However, an experiment looking for monopoles in cosmic rays has measured an interesting event which could be interpreted as a monopole. Several detectors are being built to achieve significant improvements in sensitivity for detection of quarks and monopoles. 21 refs.
Why quarks cannot be fundamental particles
Kalman, C S
2005-01-01
Many reasons why quarks should be considered composite particles are found in the book Preons by D'Souza and Kalman. One reason not found in the book is that all the quarks except for the u quark decay. The electron and the electron neutrino do not decay. A model of fundamental particles based upon the weak charge is presented.
SPONTANEOUS CP VIOLATION AND QUARK MASS AMBIGUITIES.
Energy Technology Data Exchange (ETDEWEB)
CREUTZ,M.
2004-09-21
I explore the regions of quark masses where CP will be spontaneously broken in the strong interactions. The boundaries of these regions are controlled by the chiral anomaly, which manifests itself in ambiguities in the definition of non-degenerate quark masses. In particular, the concept of a single massless quark is ill defined.
LATTICE QCD THERMODYNAMICS WITH WILSON QUARKS.
Energy Technology Data Exchange (ETDEWEB)
EJIRI,S.
2007-11-20
We review studies of QCD thermodynamics by lattice QCD simulations with dynamical Wilson quarks. After explaining the basic properties of QCD with Wilson quarks at finite temperature including the phase structure and the scaling properties around the chiral phase transition, we discuss the critical temperature, the equation of state and heavy-quark free energies.
Greenlee, H B; Abolins, M; Acharya, B S; Adams, M; Adams, T; Agelou, M; Agram, J L; Ahn, S H; Ahsan, M; Alexeev, G D; Alkhazov, G; Alton, A; Alverson, G; Alves, G A; Anastasoaie, M; Andeen, T; Anderson, S; Andrieu, B; Arnoud, Y; Askew, A; Åsman, B; Assis-Jesus, A C S; Atramentov, O; Autermann, C; Avila, C; Badaud, F; Baden, A; Baldin, B Yu; Balm, P W; Banerjee, S; Barberis, E; Bargassa, P; Baringer, P; Barnes, C; Barreto, J; Bartlett, J F; Bassler, U; Bauer, D; Bean, A; Beauceron, S; Begel, M; Bellavance, A; Beri, S B; Bernardi, G; Bernhard, R; Bertram, I; Besançon, M; Beuselinck, R; Bezzubov, V A; Bhat, P C; Bhatnagar, V; Binder, M; Biscarat, C; Black, K M; Blackler, I; Blazey, G; Blekman, F; Blessing, S; Bloch, D; Blumenschein, U; Böhnlein, A; Boeriu, O; Bolton, T A; Borcherding, F; Borissov, G; Bos, K; Bose, T; Brandt, A; Brock, R; Brooijmans, G; Bross, A; Buchanan, N J; Buchholz, D; Bühler, M; Büscher, V; Burdin, S; Burnett, T H; Busato, E; Butler, J M; Bystrický, J; Caron, S; Carvalho, W; Casey, B C K; Cason, N M; Castilla-Valdez, H; Chakrabarti, S; Chakraborty, D; Chan, K M; Chandra, A; Chapin, D; Charles, F; Cheu, E; Cho, D K; Choi, S; Choudhary, B; Christiansen, T; Christofek, L; Claes, D; Clement, B; Clément, C; Coadou, Y; Cooke, M; Cooper, W E; Coppage, D; Corcoran, M; Cothenet, A; Cousinou, M C; Cox, B; Crepe-Renaudin, S; Cristetiu, M; Cutts, D; Da Motta, H; Davies, B; Davies, G; Davis, G A; De, K; de Jong, P; De Jong, S J; De La Cruz-Burelo, E; De Oliveira Martins, C; Dean, S; Degenhardt, J D; Déliot, F; Demarteau, M; Demina, R; Demine, P; Denisov, D; Denisov, S P; Desai, S; Diehl, H T; Diesburg, M; Doidge, M; Dong, H; Doulas, S; Dudko, L V; Duflot, L; Dugad, S R; Duperrin, A; Dyer, J; Dyshkant, A; Eads, M; Edmunds, D; Edwards, T; Ellison, J; Elmsheuser, J; Elvira, V D; Eno, S; Ermolov, P; Eroshin, O V; Estrada, J; Evans, D; Evans, H; Evdokimov, A; Evdokimov, V N; Fast, J; Fatakia, S N; Feligioni, L; Ferbel, T; Fiedler, F; Filthaut, F; Fisher, W; Fisk, H E; Fleck, I; Fortner, M; Fox, H; Fu, S; Fuess, S; Gadfort, T; Galea, C F; Gallas, E; Galyaev, E; García, C; García-Bellido, A; Gardner, J; Gavrilov, V; Gay, P; Gelé, D; Gelhaus, R; Genser, K; Gerber, C E; Gershtein, Yu; Ginther, G; Golling, T; Gómez, B; Gounder, K; Goussiou, A; Grannis, P D; Greder, S; Abazov, V M; Greenwood, Z D; Gregores, E M; Gris, P; Grivaz, J F; Groer, L; Grünendahl, S; Grünewald, M W; Gurzhev, S N; Gutíerrez, G; Gutíerrez, P; Haas, A; Hadley, N J; Hagopian, S; Hall, I; Hall, R E; Han, C; Han, L; Hanagaki, K; Harder, K; Harrington, R; Hauptman, J M; Hauser, R; Hays, J; Hebbeker, T; Hedin, D; Heinmiller, J M; Heinson, A P; Heintz, U; Hensel, C; Hesketh, G; Hildreth, M D; Hirosky, R; Hobbs, J D; Hoeneisen, B; Hohlfeld, M; Hong, S J; Hooper, R; Houben, P; Hu, Y; Huang, J; Iashvili, I; Illingworth, R; Ito, A S; Jabeen, S; Jaffré, M; Jain, S; Jain, V; Jakobs, K; Jenkins, A; Jesik, R; Johns, K; Johnson, M; Jonckheere, A; Jonsson, P; Juste, A; Käfer, D; Kahl, W; Kahn, S; Kajfasz, E; Kalinin, A M; Kalk, J; Karmanov, D; Kasper, J; Kau, D; Kaur, R; Kehoe, R; Kermiche, S; Kesisoglou, S; Khanov, A; Kharchilava, A I; Kharzheev, Yu M; Kim, H; Klima, B; Klute, M; Kohli, J M; Kopal, M; Korablev, V M; Kotcher, J; Kothari, B; Koubarovsky, A; Kozelov, A V; Kozminski, J; Kryemadhi, A; Krzywdzinski, S; Kuleshov, S; Kulik, Y; Kumar, A; Kunori, S; Kupco, A; Kurca, T; Kvita, J; Lager, S; Lahrichi, N; Landsberg, G L; Lazoflores, J; Le Bihan, A C; Lebrun, P; Lee, W M; Leflat, A; Lehner, F; Leonidopoulos, C; Lévêque, J; Lewis, P; Li, J; Li, Q Z; Lima, J G R; Lincoln, D; Linn, S L; Linnemann, J T; Lipaev, V V; Lipton, R; Lobo, L; Lobodenko, A; Lokajícek, M; Lounis, A; Love, P; Lubatti, H J; Lueking, L; Lynker, M; Lyon, A L; Maciel, A K A; Madaras, R J; Mättig, P; Magass, C; Magerkurth, A; Magnan, A M; Makovec, N; Mal, P K; Malbouisson, H B; Malik, S; Malyshev, V L; Mao, H S; Maravin, Y; Martens, M; Mattingly, S E K; Mayorov, A A; McCarthy, R; McCroskey, R; Meder, D; Melanson, H L; Melnitchouk, A S; Mendes, A; Merkin, M; Merritt, K W; Meyer, A; Michaut, M; Miettinen, H; Mitrevski, J; Mokhov, N V; Molina, J; Mondal, N K; Moore, R W; Muanza, G S; Mulders, M; Mutaf, Y D; Nagy, E; Narain, M; Naumann, N A; Neal, H A; Negret, J P; Nelson, S; Neustroev, P; Nöding, C; Nomerotski, A; Novaes, S F; Nunnemann, T; Nurse, E; O'Dell, V; O'Neil, D C; Oguri, V; Oliveira, N; Oshima, N; Oteroy-Garzon, G J; Padley, P; Parashar, N; Park, S K; Parsons, J; Partridge, R; Parua, N; Patwa, A; Perea, P M; Pérez, E; Petroff, P; Petteni, M; Phaf, L; Piegaia, R; Pleier, M A; Podesta-Lerma, P L M; Podstavkov, V M; Pogorelov, Y; Pope, B G; Prado da Silva, W L; Prosper, H B; Protopopescu, S D; Qian, J; Quadt, A; Quinn, B; Rani, K J; Ranjan, K; Rapidis, P A; Ratoff, P N; Reay, N W; Reucroft, S; Rijssenbeek, M; Ripp-Baudot, I; Rizatdinova, F K; Rodrigues, R F; Royon, C; Rubinov, P; Ruchti, R; Rud, V I; Sajot, G; Sánchez-Hernández, A; Sanders, M P; Santoro, A F S; Savage, G; Sawyer, L; Scanlon, T; Schaile, A D; Schamberger, R D; Schellman, H; Schieferdecker, P; Schmitt, C; Schwartzman, A; Schwienhorst, R; Sen-Gupta, S; Severini, H; Shabalina, E; Shamim, M; Shary, V; Shchukin, A A; Shephard, W D; Shivpuri, R K; Shpakov, D; Sidwell, R A; Simák, V; Sirotenko, V I; Skubic, P L; Slattery, P F; Smith, R P; Smolek, K; Snow, G R; Snow, J; Snyder, S; Söldner-Rembold, S; Song, X; Sonnenschein, L; Sopczak, A; Sosebee, M; Soustruznik, K; Souza, M; Spurlock, B; Stanton, N R; Stark, J; Steele, J; Stevenson, K; Stolin, V; Stone, A; Stoyanova, D A; Strandberg, J; Strang, M A; Strauss, M; Ströhmer, R; Strom, D; Strovink, M; Stutte, L; Sumowidagdo, S; Sznajder, A; Talby, M; Tamburello, P; Taylor, W; Telford, P; Temple, J; Thomas, E; Thooris, B; Tomoto, M; Toole, T; Torborg, J; Towers, S; Trefzger, T; Trincaz-Duvoid, S; Tuchming, B; Tully, C; Turcot, A S; Tuts, P M; Uvarov, L; Uvarov, S; Uzunyan, S; Vachon, B; Van Kooten, R; Van Leeuwen, W M; Varelas, N; Varnes, E W; Vartapetian, A H; Vasilyev, I A; Vaupel, M; Verdier, P; Vertogradov, L S; Verzocchi, M; Villeneuve-Séguier, F; Vlimant, J R; Von Törne, E; Vreeswijk, M; Vu-Anh, T; Wahl, H D; Walker, R; Wang, L; Wang, Z M; Warchol, J; Watts, G; Wayne, M; Weber, M; Weerts, H; Wegner, M; Wermes, N; White, A; White, V; Wicke, D; Wijngaarden, D A; Wilson, G W; Wimpenny, S J; Wittlin, J; Wobisch, M; Womersley, J; Wood, D R; Wyatt, T R; Xu, Q; Xuan, N; Yacoob, S Y; Yamada, R; Yan, M; Yasuda, T; Yatsunenko, Y A; Yen, Y; Yip, K; Yoo, H D; Youn, S W; Yu, J; Yurkewicz, A; Zabi, A; Zatserklyaniy, A; Zdrazil, M; Zeitnitz, C; Zhang, D; Zhang, X; Zhao, T; Zhao, Z; Zhou, B; Zhu, J; Zielinski, M; Zieminska, D; Zieminski, A; Zitoun, R; Zutshi, V; Zverev, E G
2005-01-01
In this talk I will present recent preliminary results from the D0 experiment from Tevatron Run II ($p\\bar p$ collisions at $\\sqrt{s} = 1.96$ TeV). The results presented in this talk include top quark pair production cross section, top quark mass, and upper limits on single top quark production.
In-medium kaon and antikaon properties in the quark-meson coupling model
Tsushima, K; Thomas, A W; Wright, S V
1998-01-01
The properties of the kaon, $K$, and antikaon, $\\kbar$, in nuclear medium are studied in the quark-meson coupling (QMC) model. Employing a constituent quark-antiquark (MIT bag model) picture, their excitation energies in a nuclear medium at zero momentum are calculated within mean field approximation. The scalar, and the vector mesons are assumed to couple directly to the nonstrange quarks and antiquarks in the $K$ and $\\kbar$ mesons. It is demonstrated that the $\\rho$ meson induces different mean field potentials for each member of the isodoublets, $K$ and $\\kbar$, when they are embedded in asymmetric nuclear matter. Furthermore, it is also shown that this $\\rho$ meson potential is repulsive for the $K^-$ meson in matter with a neutron excess, and renders $K^-$ condensation less likely to occur.
Semileptonic Decays of Heavy Omega Baryons in a Quark Model
Energy Technology Data Exchange (ETDEWEB)
Muslema Pervin; Winston Roberts; Simon Capstick
2006-03-24
The semileptonic decays of {Omega}{sub c} and {Omega}{sub b} are treated in the framework of a constituent quark model developed in a previous paper on the semileptonic decays of heavy {Lambda} baryons. Analytic results for the form factors for the decays to ground states and a number of excited states are evaluated. For {Omega}{sub b} to {Omega}{sub c} the form factors obtained are shown to satisfy the relations predicted at leading order in the heavy-quark effective theory at the non-recoil point. A modified fit of nonrelativistic and semirelativistic Hamiltonians generates configuration-mixed baryon wave functions from the known masses and the measured {Lambda}{sub c}{sup +} {yields} {Lambda}e{sup +}{nu} rate, with wave functions expanded in both harmonic oscillator and Sturmian bases. Decay rates of {Omega}{sub b} to pairs of ground and excited {Omega}{sub c} states related by heavy-quark symmetry calculated using these configuration-mixed wave functions are in the ratios expected from heavy-quark effective theory, to a good approximation. Our predictions for the semileptonic elastic branching fraction of {Omega}{sub Q} vary minimally within the models we use. We obtain an average value of (84 {+-} 2%) for the fraction of {Omega}{sub c} {yields} {Xi}{sup (*)} decays to ground states, and 91% for the fraction of {Omega}{sub c} {yields} {Omega}{sup (*)} decays to the ground state {Omega}. The elastic fraction of {Omega}{sub b} {yields} {Omega}{sub c} ranges from about 50% calculated with the two harmonic-oscillator models, to about 67% calculated with the two Sturmian models.
Decay constants in the heavy quark limit in models à la Bakamjian and Thomas
Morénas, V; Oliver, L; Pène, O; Raynal, J C
1998-01-01
In quark models à la Bakamjian and Thomas, that yield covariance and Isgur-Wise scaling of form factors in the heavy quark limit, we compute the decay constants $f^{(n)}$ and $f^{(n)}_{1/2}$ of S-wave and P-wave mesons composed of heavy and light quarks. Heavy quark limit scaling $\\sqrt{M} f = Cst$ is obtained, and it is shown that this class of models satisfies the sum rules involving decay constants and Isgur-Wise functions recently formulated by us in the heavy quark limit of QCD. Moreover, the model also satisfies the selection rules of the type $f^{(n)}_{3/2} = 0$ that must hold in this limit. We discuss different Ansätze for the dynamics of the mass operator at rest. For non-relativistic kinetic energies ${p^2 \\over 2m}$ the decay constants are finite even if the potential $V(r)$ has a Coulomb part. For the relativistic form $\\sqrt{p^2 + m^2}$, the S-wave decay constants diverge if there is a Coulomb singularity. Using phenomenological models of the spectrum with relativistic kinetic energy and regula...
Exotic-Hadron Signature by Constituent-Counting Rule in Perturbative QCD
Chang, Wen-Chen; Kumano, S; Sekihara, T
2016-01-01
We explain a method to find internal quark configurations of exotic hadron candidates by using the constituent counting rule. The counting rule was theoretically predicted in perturbative QCD for hard exclusive hadron reactions, and it has been tested in experiments for stable hadrons including compound systems of hadrons such as the deuteron, $^3$H, and $^3$He. It indicates that the cross section scales as $d\\sigma /dt \\sim 1/s^{n-2}$, where $s$ is the center-of-mass energy squared and $n$ is the total number of constituents. We apply this method for finding internal configurations of exotic hadron candidates, especially $\\Lambda (1405)$. There is a possibility that $\\Lambda (1405)$ could be five-quark state or a $\\bar K N$ molecule, and scaling properties should be different between the ordinary three-quark state or five-quark one. We predict such a difference in $\\pi^- + p \\to K^0 + \\Lambda (1405)$, and it could be experimentally tested, for example, at J-PARC. On the other hand, there are already measurem...
Top quark physics with the CMS experiment
Directory of Open Access Journals (Sweden)
Cuevas Javier
2014-04-01
Full Text Available An overview of recent top quark measurements in proton-proton collisions at √s = 7 and 8 TeV in data collected with the CMS experiment at the LHC, using a data sample collected during the years 2011 and 2012 is presented. Measurements of top quark pair production cross sections in several top quark final states are reported, as well as electroweak production of single top quarks in both t-and tW-channels. The mass of the top quark is estimated by different methods.
Top-Quark Physics Results From LHC
INSPIRE-00214275
2012-01-01
The top-quark is a fundamental element of the physics program at the Large Hadron Collider (LHC). We review the current status of the top-quark measurements performed by ATLAS and CMS experiments in pp collisions at sqrt(s)=7 TeV with a focus on the recent results of the top-quark production rates and the measurements of the mass and other properties of the top-quark. We will also describe the recent searches for physics beyond the Standard Model in the top-quark sector.
Quark sea asymmetry of the nucleon
Mírez, Carlos; Tomio, Lauro; Trevisan, L. A.; Frederico, T.
2010-02-01
The light anti-quark and quark distribution in the proton, as well as the neutron to proton ratio of the structure functions, extracted from experimental data, are well fitted by a statistical model of linear-confined quarks. The parameters of the model are given by a temperature, which is adjusted by the Gottfried sum-rule violation, and two chemical potentials given by the corresponding up ( u) and down ( d) quark normalizations in the nucleon. The quark energy levels are generated by a relativistic linear-confined scalar plus vector potential.
Phenomenology with Lattice NRQCD b Quarks
Colquhoun, Brian; Dowdall, Rachel J; Koponen, Jonna; Lepage, G Peter; Lytle, Andrew T
2015-01-01
The HPQCD collaboration has used radiatively-improved NonRelativistic QCD (NRQCD) for $b$ quarks in bottomonium to determine the decay rate of $\\Upsilon$ and $\\Upsilon^\\prime$ mesons to leptons in lattice QCD. Using time-moments of vector bottomonium current-current correlators, we are also able to determine the $b$ quark mass in the $\\overline{\\mathrm{MS}}$ scheme. We use the same NRQCD $b$ quarks and Highly Improved Staggered Quark (HISQ) light quarks -- with masses down to their physical values -- to give a complete picture of heavy-light meson decay constants including those for vector mesons. We also study the semileptonic $B\\rightarrow\\pi\\ell\
Heavy quark colorimetry of QCD matter
Dokshitzer, Yu L; Dokshitzer, Yu.L.
2001-01-01
We consider propagation of heavy quarks in QCD matter. Because of large quark mass, the radiative quark energy loss appears to be qualitatively different from that of light quarks at all energies of practical importance. Finite quark mass effects lead to an in-medium enhancement of the heavy-to-light D/\\pi ratio at moderately large (5--10 GeV) transverse momenta. For hot QCD matter a large enhancement is expected, whose magnitude and shape are exponentially sensitive to the density of colour charges in the medium.
Triminimal parametrization of quark mixing matrix
He, Xiao-Gang; Li, Shi-Wen; Ma, Bo-Qiang
2008-12-01
Starting from a new zeroth order basis for quark mixing (CKM) matrix based on the quark-lepton complementarity and the tribimaximal pattern of lepton mixing, we derive a triminimal parametrization of a CKM matrix with three small angles and a CP-violating phase as its parameters. This new triminimal parametrization has the merits of fast convergence and simplicity in application. With the quark-lepton complementary relations, we derive relations between the two unified triminimal parametrizations for quark mixing obtained in this work and for lepton mixing obtained by Pakvasa-Rodejohann-Weiler. Parametrization deviating from quark-lepton complementarity is also discussed.
Young, Robert D.
1973-01-01
Discusses the charge independence, wavefunctions, magnetic moments, and high-energy scattering of hadrons on the basis of group theory and nonrelativistic quark model with mass spectrum calculated by first-order perturbation theory. The presentation is explainable to advanced undergraduate students. (CC)
Kim, S. B.
1995-08-01
Top quark production is observed in{bar p}p collisions at{radical}s= 1.8 TeV at the Fermilab Tevatron. The Collider Detector at Fermilab (CDF) and D{O} observe signals consistent with t{bar t} to WWb{bar b}, but inconsistent with the background prediction by 4.8{sigma} (CDF), 4.6a (D{O}). Additional evidence for the top quark Is provided by a peak in the reconstructed mass distribution. The kinematic properties of the excess events are consistent with the top quark decay. They measure the top quark mass to be 176{plus_minus}8(stat.){plus_minus}10(sys.) GeV/c{sup 2} (CDF), 199{sub -21}{sup+19}(stat.){plus_minus}22(sys.) GeV/c{sup 2} (D{O}), and the t{bar t} production cross section to be 6.8{sub -2.4}{sup+3.6}pb (CDF), 6.4{plus_minus}2.2 pb (D{O}).
Hydrodynamics of a quark droplet
DEFF Research Database (Denmark)
Bjerrum-Bohr, Johan J.; Mishustin, Igor N.; Døssing, Thomas
2012-01-01
We present a simple model of a multi-quark droplet evolution based on the hydrodynamical description. This model includes collective expansion of the droplet, effects of the vacuum pressure and surface tension. The hadron emission from the droplet is described following Weisskopf's statistical...
Young, Robert D.
1973-01-01
Discusses the charge independence, wavefunctions, magnetic moments, and high-energy scattering of hadrons on the basis of group theory and nonrelativistic quark model with mass spectrum calculated by first-order perturbation theory. The presentation is explainable to advanced undergraduate students. (CC)
Energy Technology Data Exchange (ETDEWEB)
Barberis, Emanuela; /Northeastern U.
2006-05-01
A summary of the results on the measurement of the Top Quark mass and the study of the kinematics of the t{bar t} system at the Tevatron collider is presented here. Results from both the CDF and D0 collaborations are reported.
Lebed, Richard F; Swanson, Eric S
2016-01-01
This review presents an overview of the remarkable progress in the field of heavy-quark exotic hadrons over the past 15 years. It seeks to be pedagogical rather than exhaustive, summarizing both the progress and specific results of experimental discoveries, and the variety of theoretical approaches designed to explain these new states.
2003-01-01
Fitted with new state-of-the-art silicon detectors, NA60 is prepared to study the phase transition from confined hadronic matter to a deconfined (free) quark-gluon plasma, a state of matter which probably existed an instant after the Big Bang.
Heavy Quark Asymmetries at LEP
Halley, A W
1999-01-01
Measurements of b and c quark asymmetries using data collected at LEP 1 are described. The relative merits of each of the individual techniques used is emphasised as is the most profitable way of combining them. Effects of radiative corrections are discussed, together with the impact of these measurements on global electroweak fits used to estimate the expected mass of the Higgs boson.
Quark masses without Yukawa hierarchies
Energy Technology Data Exchange (ETDEWEB)
Fanchiotti, H.; Garcia-Canal, C. [Plata Univ. Nacional, Laboratorio de Fisica Teorica, Dept. de Fisica, Facultad de Ciencias Exactas, La Plata (Argentina); Ponce, W.A. [Antioquia Univ., Instituto de Fisica, Colombia La (Argentina)
2005-12-15
A model based on the local gauge group SU(3){sub c}*SU(3){sub L}*U(1){sub X} without particles with exotic electric charges is shown to be able to provide the quark mass spectrum and their mixing, by means of universal see-saw mechanisms, avoiding a hierarchy in the Yukawa coupling constants. (authors)
Dilepton production by dynamical quasiparticles in the strongly interacting quark gluon plasma
Linnyk, O
2010-01-01
The dilepton production by the constituents of the strongly interacting quark-gluon-plasma (sQGP) is addressed. In order to make quantitative predictions at realistically low plasma temperatures (O(T_c)), experimentally relevant low dilepton mass (O(1 GeV)) and strong coupling (alphaS=0.5-1), we take into account not only the higher order pQCD reaction mechanisms, but also the non-perturbative spectral functions (off-shellness) and self-energies of the quarks, anti-quarks and gluons thus going beyond the leading twist. For this purpose, our calculations utilize parametrizations of the non-perturbative propagators for quarks and gluons provided by the dynamical quasi-particle model (DQPM) matched to reproduce lattice data. The DQPM describes QCD properties in terms of single-particle Green's functions (in the sense of a two-particle irreducible approach) and leads to the notion of the constituents of the sQGP being effective quasiparticles, which are massive and have broad spectral functions (due to large inte...
Brown, Laurie Mark; Dresden, Max; Hoddeson, Lillian
2009-01-01
Part I. Introduction; 1. Pions to quarks: particle physics in the 1950s Laurie M Brown, Max Dresden and Lillian Hoddeson; 2. Particle physics in the early 1950s Chen Ning Yang; 3. An historian's interest in particle physics J. L. Heilbron; Part II. Particle discoveries in cosmic rays; 4. Cosmic-ray cloud-chamber contributions to the discovery of the strange particles in the decade 1947-1957 George D. Rochester; 5. Cosmic-ray work with emulsions in the 1940s and 1950s Donald H. Perkins; Part III. High-energy nuclear physics; Learning about nucleon resonances with pion photoproduction Robert L. Walker; 7. A personal view of nucleon structure as revealed by electron scattering Robert Hofstadter; 8. Comments on electromagnetic form factors of the nucleon Robert G. Sachs and Kameshwar C. Wali; Part IV. The new laboratory; 9. The making of an accelerator physicist Matthew Sands; 10. Accelerator design and construction in the 1950s John P. Blewett; 11. Early history of the Cosmotron and AGS Ernest D. Courant; 12. Panel on accelerators and detectors in the 1950s Lawrence W. Jones, Luis W. Alvarez, Ugo Amaldi, Robert Hofstadter, Donald W. Kerst, Robert R. Wilson; 13. Accelerators and the Midwestern Universities Research Association in the 1950s Donald W. Kerst; 14. Bubbles, sparks and the postwar laboratory Peter Galison; 15. Development of the discharge (spark) chamber in Japan in the 1950s Shuji Fukui; 16. Early work at the Bevatron: a personal account Gerson Goldhaber; 17. The discovery of the antiproton Owen Chamberlain; 18. On the antiproton discovery Oreste Piccioni; Part V. The Strange Particles; 19. The hydrogen bubble chamber and the strange resonances Luis W. Alvarez; 20. A particular view of particle physics in the fifties Jack Steinberger; 21. Strange particles William Chinowsky; 22. Strange particles: production by Cosmotron beams as observed in diffusion cloud chambers William B. Fowler; 23. From the 1940s into the 1950s Abraham Pais; Part VI. Detection of the
Covariant diagrams for one-loop matching
Zhang, Zhengkang
2016-01-01
We present a diagrammatic formulation of recently-revived covariant functional approaches to one-loop matching from an ultraviolet (UV) theory to a low-energy effective field theory. Various terms following from a covariant derivative expansion (CDE) are represented by diagrams which, unlike conventional Feynman diagrams, involve gauge-covariant quantities and are thus dubbed "covariant diagrams." The use of covariant diagrams helps organize and simplify one-loop matching calculations, which we illustrate with examples. Of particular interest is the derivation of UV model-independent universal results, which reduce matching calculations of specific UV models to applications of master formulas. We show how such derivation can be done in a more concise manner than the previous literature, and discuss how additional structures that are not directly captured by existing universal results, including mixed heavy-light loops, open covariant derivatives, and mixed statistics, can be easily accounted for.
ISSUES IN NEUTRON CROSS SECTION COVARIANCES
Energy Technology Data Exchange (ETDEWEB)
Mattoon, C.M.; Oblozinsky,P.
2010-04-30
We review neutron cross section covariances in both the resonance and fast neutron regions with the goal to identify existing issues in evaluation methods and their impact on covariances. We also outline ideas for suitable covariance quality assurance procedures.We show that the topic of covariance data remains controversial, the evaluation methodologies are not fully established and covariances produced by different approaches have unacceptable spread. The main controversy is in very low uncertainties generated by rigorous evaluation methods and much larger uncertainties based on simple estimates from experimental data. Since the evaluators tend to trust the former, while the users tend to trust the latter, this controversy has considerable practical implications. Dedicated effort is needed to arrive at covariance evaluation methods that would resolve this issue and produce results accepted internationally both by evaluators and users.
Parameter inference with estimated covariance matrices
Sellentin, Elena
2015-01-01
When inferring parameters from a Gaussian-distributed data set by computing a likelihood, a covariance matrix is needed that describes the data errors and their correlations. If the covariance matrix is not known a priori, it may be estimated and thereby becomes a random object with some intrinsic uncertainty itself. We show how to infer parameters in the presence of such an estimated covariance matrix, by marginalising over the true covariance matrix, conditioned on its estimated value. This leads to a likelihood function that is no longer Gaussian, but rather an adapted version of a multivariate $t$-distribution, which has the same numerical complexity as the multivariate Gaussian. As expected, marginalisation over the true covariance matrix improves inference when compared with Hartlap et al.'s method, which uses an unbiased estimate of the inverse covariance matrix but still assumes that the likelihood is Gaussian.
ISSUES IN NEUTRON CROSS SECTION COVARIANCES
Energy Technology Data Exchange (ETDEWEB)
Mattoon, C.M.; Oblozinsky,P.
2010-04-30
We review neutron cross section covariances in both the resonance and fast neutron regions with the goal to identify existing issues in evaluation methods and their impact on covariances. We also outline ideas for suitable covariance quality assurance procedures.We show that the topic of covariance data remains controversial, the evaluation methodologies are not fully established and covariances produced by different approaches have unacceptable spread. The main controversy is in very low uncertainties generated by rigorous evaluation methods and much larger uncertainties based on simple estimates from experimental data. Since the evaluators tend to trust the former, while the users tend to trust the latter, this controversy has considerable practical implications. Dedicated effort is needed to arrive at covariance evaluation methods that would resolve this issue and produce results accepted internationally both by evaluators and users.
Treatment Effects with Many Covariates and Heteroskedasticity
DEFF Research Database (Denmark)
Cattaneo, Matias D.; Jansson, Michael; Newey, Whitney K.
The linear regression model is widely used in empirical work in Economics. Researchers often include many covariates in their linear model specification in an attempt to control for confounders. We give inference methods that allow for many covariates and heteroskedasticity. Our results are obtai......The linear regression model is widely used in empirical work in Economics. Researchers often include many covariates in their linear model specification in an attempt to control for confounders. We give inference methods that allow for many covariates and heteroskedasticity. Our results...... then propose a new heteroskedasticity consistent standard error formula that is fully automatic and robust to both (conditional) heteroskedasticity of unknown form and the inclusion of possibly many covariates. We apply our findings to three settings: (i) parametric linear models with many covariates, (ii...
Irving, A C; Michael, C; Sharkey, K J; Wittig, H
2001-01-01
We report on determinations of the low-energy constants alpha5 and alpha8 in the effective chiral Lagrangian at O(p^4), using lattice simulations with N_f=2 flavours of dynamical quarks. Precise knowledge of these constants is required to test the hypothesis whether or not the up-quark is massless. Our results are obtained by studying the quark mass dependence of suitably defined ratios of pseudoscalar meson masses and matrix elements. Although comparisons with an earlier study in the quenched approximation reveal small qualitative differences in the quark mass behaviour, numerical estimates for alpha5 and alpha8 show only a weak dependence on the number of dynamical quark flavours. Our results disfavour the possibility of a massless up-quark, provided that the quark mass dependence in the physical three-flavour case is not fundamentally different from the two-flavour case studied here.
State of matter for quark stars
Lai, X Y
2009-01-01
It depends on the state of matter at supra-nuclear density to model pulsar's structure, which is unfortunately not certain due to the difficulties in physics. In cold quark matter at realistic baryon densities of compact stars (with an average value of $\\sim 2-3\\rho_0$), the interaction between quarks is so strong that they would condensate in position space to form quark-clusters. We argue that quarks in quark stars are grouped in clusters, then we apply two phenomenological models for quark stars, the polytropic model and Lennard-Jones model. Both of the two models have stiffer EoS, and larger maximum mass for quark stars (larger than 2 $M_\\odot$). The gravitational energy releases during the AIQ process could explain the observed energy of three supergiant flares from soft gamma-ray repeaters ($\\sim 10^{47}$ ergs).
The effect of dynamical quark mass on the calculation of a strange quark star's structure
Institute of Scientific and Technical Information of China (English)
Gholam Hossein Bordbar; Babak Ziaei
2012-01-01
We discuss the dynamical behavior of strange quark matter components,in particular the effects of density dependent quark mass on the equation of state of strange quark matter.The dynamical masses of quarks are computed within the Nambu-Jona-Lasinio model,then we perform strange quark matter calculations employing the MIT bag model with these dynamical masses.For the sake of comparing dynamical mass interaction with QCD quark-quark interaction,we consider the one-gluon-exchange term as the effective interaction between quarks for the MIT bag model.Our dynamical approach illustrates an improvement in the obtained equation of state values.We also investigate the structure of the strange quark star using TolmanOppenheimer-Volkoff equations for all applied models.Our results show that dynamical mass interaction leads to lower values for gravitational mass.
Randall, Lisa
1994-01-01
We present a detailed analysis of the use of heavy quark fragmentation into heavy hadrons for testing the heavy quark effective theory through comparison of the measured fragmentation parameters of the c and b quarks. Our analysis is entirely model independent. We interpret the known perturbative evolution in a way useful for exploiting heavy quark symmetry at low energy. We first show consistency with perturbative QCD scaling for measurements done solely with c quarks. We then apply the perturbative analysis and the heavy quark expansion to relate measurements from ARGUS and LEP. We place bounds on a nonperturbative quark mass suppressed parameter, and compare the values for the b and c quarks. We find consistency with the heavy quark expansion but fairly sizable QCD uncertainties. We also suggest that one might reduce the systematic uncertainty in the result by not extrapolating to low z.
Eigenvalue variance bounds for covariance matrices
Dallaporta, Sandrine
2013-01-01
This work is concerned with finite range bounds on the variance of individual eigenvalues of random covariance matrices, both in the bulk and at the edge of the spectrum. In a preceding paper, the author established analogous results for Wigner matrices and stated the results for covariance matrices. They are proved in the present paper. Relying on the LUE example, which needs to be investigated first, the main bounds are extended to complex covariance matrices by means of the Tao, Vu and Wan...
Radiative decays of $1^{++}$ heavy mesons in the covariant light-front approach
Shi, Yan-Liang
2016-01-01
We calculate the predicted width for the radiative decay of a $1^{++}$ heavy meson via the channel $1^{++} \\to 1^{--} +\\gamma$ in the covariant light-front quark model. Specifically, we compute the decay widths for $\\chi_{c1}(1P) \\to J/\\psi + \\gamma$ and $\\chi_{b1}(nP) \\to \\Upsilon(n'S) + \\gamma$. The results are compared with experimental data and with predictions from calculations based on nonrelativistic models and their extensions to include relativistic effects.
Inclusive Single-Spin Asymmetries, Quark-Photon, and Quark-Quark Correlations
Burkardt, Matthias
2016-01-01
We consider quark-photon correlations that have been proposed as a source for single-spin asymmetries in inclusive deep-inelastic scattering. A new sum rule for these correlators is derived and its phenomenological consequences are discussed. The results are interpreted within the context of an intuitive 'electrodynamic lensing' picture.
Leibbrandt, George; Leibbrandt, George; Williams, Jimmy D.
2000-01-01
The complete two-loop correction to the quark propagator, consisting of the spider, rainbow, gluon bubble and quark bubble diagrams, is evaluated in the noncovariant light-cone gauge (lcg). (The overlapping self-energy diagram had already been computed.) The chief technical tools include the powerful matrix integration technique, the n^*-prescription for the spurious poles of 1/qn, and the detailed analysis of the boundary singularities in five- and six-dimensional parameter space. It is shown that the total divergent contribution to the two-loop correction Sigma_2 contains both covariant and noncovariant components, and is a local function of the external momentum p, even off the mass-shell, as all nonlocal divergent terms cancel exactly. Consequently, both the quark mass and field renormalizations are local. The structure of Sigma_2 implies a quark mass counterterm of the form $\\delta m (lcg) = m\\tilde\\alpha_s C_F(3+\\tilde\\alpha_sW) + {\\rm O} (\\tilde\\alpha_s^3)$, the dimensional regulator epsilon, and on th...
Isospin properties of quark matter from a 3-flavor NJL model
Liu, He; Xu, Jun; Chen, Lie-Wen; Sun, Kai-Jia
2016-09-01
We have studied the properties of hot and dense quark matter based on the 3-flavor Nambu-Jona-Lasinio (NJL) model as well as its Polyakov-loop extension (pNJL) with scalar-isovector and vector-isovector couplings. Provided a considerable large isospin asymmetry or isospin chemical potential, isospin splittings of constituent mass, chiral phase transition boundary, and critical point for u and d quarks can be observed for positive isovector coupling constants but are suppressed for negative ones. The quark matter symmetry energy decreases with the increasing isovector coupling constant, and is mostly enhanced in the pNJL model than in the NJL model. A positive scalar-isovector coupling constant is more likely to lead to an unstable isospin asymmetric quark matter. The isovector coupling has been further found to affect particle fractions as well as the equation of state in hybrid stars. Possible effects on the isospin properties of quark matter have also been discussed if the strangeness sector is further broken among the flavor symmetry.
Maximal Wavelength of Confined Quarks and Gluons and Properties of Quantum Chromodynamics
Energy Technology Data Exchange (ETDEWEB)
Brodsky, Stanley J.; /SLAC /YITP, Stony Brook /Durham U.; Shrock, Robert; /YITP, Stony Brook
2008-08-01
Because quarks and gluons are confined within hadrons, they have a maximum wavelength of order the confinement scale. Propagators, normally calculated for free quarks and gluons using Dyson-Schwinger equations, are modified by bound-state effects in close analogy to the calculation of the Lamb shift in atomic physics. Because of confinement, the effective quantum chromodynamic coupling stays finite in the infrared. The quark condensate which arises from spontaneous chiral symmetry breaking in the bound state Dyson-Schwinger equation is the expectation value of the operator {bar q}q evaluated in the background of the fields of the other hadronic constituents, in contrast to a true vacuum expectation value. Thus quark and gluon condensates reside within hadrons. The effects of instantons are also modified. We discuss the implications of the maximum quark and gluon wavelength for phenomena such as deep inelastic scattering and annihilation, the decay of heavy quarkonia, jets, and dimensional counting rules for exclusive reactions. We also discuss implications for the zero-temperature phase structure of a vectorial SU(N) gauge theory with a variable number N{sub f} of massless fermions.
Results on top-quark physics and top-quark-like signatures by CMS
Chabert, Eric Christian
2017-01-01
This report reviews the results obtained by the CMS Collaboration on top quark physics, focusing on the latest ones based on p--p collisions provided by the LHC at $\\sqrt{s}$=13 TeV during Run II. It covers measurements of single-top, top quark pairs and associated productions as well as measurements of top quark properties.Finally several beyond the standard model searches involving top quark in the final states are presented such as searches for supersymmetry in the third generation, heavy resonances decaying into a top quark pair, or dark matter produced in association to a single-top or a top quark pair.
QCD phase transition with chiral quarks and physical quark masses.
Bhattacharya, Tanmoy; Buchoff, Michael I; Christ, Norman H; Ding, H-T; Gupta, Rajan; Jung, Chulwoo; Karsch, F; Lin, Zhongjie; Mawhinney, R D; McGlynn, Greg; Mukherjee, Swagato; Murphy, David; Petreczky, P; Renfrew, Dwight; Schroeder, Chris; Soltz, R A; Vranas, P M; Yin, Hantao
2014-08-22
We report on the first lattice calculation of the QCD phase transition using chiral fermions with physical quark masses. This calculation uses 2+1 quark flavors, spatial volumes between (4 fm)(3) and (11 fm)(3) and temperatures between 139 and 196 MeV. Each temperature is calculated at a single lattice spacing corresponding to a temporal Euclidean extent of N(t) = 8. The disconnected chiral susceptibility, χ(disc) shows a pronounced peak whose position and height depend sensitively on the quark mass. We find no metastability near the peak and a peak height which does not change when a 5 fm spatial extent is increased to 10 fm. Each result is strong evidence that the QCD "phase transition" is not first order but a continuous crossover for m(π) = 135 MeV. The peak location determines a pseudocritical temperature T(c) = 155(1)(8) MeV, in agreement with earlier staggered fermion results. However, the peak height is 50% greater than that suggested by previous staggered results. Chiral SU(2)(L) × SU(2)(R) symmetry is fully restored above 164 MeV, but anomalous U(1)(A) symmetry breaking is nonzero above T(c) and vanishes as T is increased to 196 MeV.
Discovery of single top quark production
Gillberg, Dag
2011-01-01
The top quark is by far the heaviest known fundamental particle with a mass nearing that of a gold atom. Because of this strikingly high mass, the top quark has several unique properties and might play an important role in electroweak symmetry breaking—the mechanism that gives all elementary particles mass. Creating top quarks requires access to very high energy collisions, and at present only the Tevatron collider at Fermilab is capable of reaching these energies. Until now, top quarks have only been observed produced in pairs via the strong interaction. At hadron colliders, it should also be possible to produce single top quarks via the electroweak interaction. Studies of single top quark production provide opportunities to measure the top quark spin, how top quarks mix with other quarks, and to look for new physics beyond the standard model. Because of these interesting properties, scientists have been looking for single top quarks for more than 15 years. This thesis presents the first discovery of singl...
Institute of Scientific and Technical Information of China (English)
SUN Le-Xue; WANG Rui-Qin; SONG Jun; SHAO Feng-Lan
2012-01-01
The quark combination mechanism of hadron production is applied to nucleus-nucleus collisions at the CERN Super Proton Synchrotron (SPS) and the BNL Alternating Gradient Synchrotron (AGS).The rapidity spectra of identified hadrons and their spectrum widths are studied.The data of π-,K±,φ,A,(A),Ξ- and Ξ+ at 80 and 40 A GeV,and in particular at 30 and 20 A GeV where the onset of deconfinement is suggested to happen,are consistently described by the quark combination model.However,at AGS 11.6 A GeV below the onset,the π±,K± and A spectra cannot be simultaneously explained,indicating the disappearance of the intrinsic correlation of their production in the constituent quark level.The collision-energy dependence of the rapidity spectrum widths of the constituent quarks,and the strangeness of the hot and dense quark matter produced in heavy ion collisions,are obtained and discussed.
A Study of Quark Fragmentation Using Kaons Produced in Association with Prompt $D_s^±/D^±$ Mesons
Energy Technology Data Exchange (ETDEWEB)
Singh, Niharika Ranjan [Purdue Univ., West Lafayette, IN (United States)
2012-01-01
Quarks are considered to be the fundamental constituents of hadronic matter, but they have never been observed as free particles. When quarks are produced at high energy colliders, they quickly form bound colorless states, which then decay to produce the particles observed in experiments. The process by which an initially free quark combines with other quarks to form a hadronic particle is called quark fragmentation and has been described using phenomenological models since quarks were first proposed. Since then, several models have been developed to describe the quark fragmentation phenomenon, and these have been tuned to reproduce many average properties of hadrons produced in high energy collisions. In this dissertation, we describe an analysis that probes the properties of particles produced in association with a hadron containing a charm quark that provides a way, for the first time, to study what is thought of as the second particle produced in the process of heavy quar k fragmentation. Data from proton anti-proton collisions was used to carry out this research, which were collected with the CDF II detector at the Fermilab Tevatron and corresponds to 360/pb^{-1} of integrated luminosity. We reconstruct $D_s^±$ and $D^±$ mesons, which contain charm quarks, and identify the kaons produced in association with them. The kinematic properties of these kaons are compared with predictions of the fragmentation models implemented in the PYTHIA and HERWIG event generators. We find that kaon production in association with $D_s^±$ mesons is enhanced at levels that are in agreement with the fragmentation models but observe differences in production rates of kaons that are produced later in the fragmentation process.
Covariance structure models of expectancy.
Henderson, M J; Goldman, M S; Coovert, M D; Carnevalla, N
1994-05-01
Antecedent variables under the broad categories of genetic, environmental and cultural influences have been linked to the risk for alcohol abuse. Such risk factors have not been shown to result in high correlations with alcohol consumption and leave unclear an understanding of the mechanism by which these variables lead to increased risk. This study employed covariance structure modeling to examine the mediational influence of stored information in memory about alcohol, alcohol expectancies in relation to two biologically and environmentally driven antecedent variables, family history of alcohol abuse and a sensation-seeking temperament in a college population. We also examined the effect of criterion contamination on the relationship between sensation-seeking and alcohol consumption. Results indicated that alcohol expectancy acts as a significant, partial mediator of the relationship between sensation-seeking and consumption, that family history of alcohol abuse is not related to drinking outcome and that overlap in items on sensation-seeking and alcohol consumption measures may falsely inflate their relationship.
Effect of a Small Current Quark Mass on Bag Constant
Institute of Scientific and Technical Information of China (English)
ZONG Hong-Shi; FENG Hong-Tao; SUN Wei-Min; DING Xiao-Ping; PING Jia-Lun
2004-01-01
A method for obtaining the small current quark mass effect on the dressed quark propagator within the Dyson-Schwinger approach is developed. From this the small current quark mass dependence of the bag constant is evaluated. It is found that the bag constant decreases with the increasing current quark mass and the contribution of the current quark mass cannot be dropped.
Effect of a Small Current Quark Mass on Bag Constant
Institute of Scientific and Technical Information of China (English)
ZONGHong-Shi; FENGHong-Tao; SUNWei-Min; DINGXiao-Ping; PINGJia-Lun
2004-01-01
A method for obtaining the small current quark mass effect on the dressed quark propagator within the Dyson Schwinger approach is developed. From this the small current quark mass dependence of the bag constant is evaluated. It is found that the bag constant decreases with the increasing current quark mass and the contribution of the current quark mass cannot be dropped.
On the Origin of Gravitational Lorentz Covariance
Khoury, Justin; Tolley, Andrew J
2013-01-01
We provide evidence that general relativity is the unique spatially covariant effective field theory of the transverse, traceless graviton degrees of freedom. The Lorentz covariance of general relativity, having not been assumed in our analysis, is thus plausibly interpreted as an accidental or emergent symmetry of the gravitational sector.
COVARIATION BIAS AND THE RETURN OF FEAR
de Jong, Peter; VANDENHOUT, MA; MERCKELBACH, H
1995-01-01
Several studies have indicated that phobic fear is accompanied by a covariation bias, i.e. that phobic Ss tend to overassociate fear relevant stimuli and aversive outcomes. Such a covariation bias seems to be a fairly direct and powerful way to confirm danger expectations and enhance fear. Therefore
Covariant derivative of fermions and all that
Shapiro, Ilya L
2016-01-01
We present detailed pedagogical derivation of covariant derivative of fermions and some related expressions, including commutator of covariant derivatives and energy-momentum tensor of a free Dirac field. The text represents a part of the initial chapter of a one-semester course on semiclassical gravity.
Quark Confinement and Force Unification
Directory of Open Access Journals (Sweden)
Stone R. A. Jr.
2010-04-01
Full Text Available String theory had to adopt a bi-scale approach in order to produce the weakness of gravity. Taking a bi-scale approach to particle physics along with a spin connection produces 1 the measured proton radius, 2 a resolution of the multiplicity of measured weak angle values 3 a correct theoretical value for the Z 0 4 a reason that h is a constant and 5 a “neutral current” source. The source of the “neutral current” provides 6 an alternate solution to quark confinement, 7 produces an effective r like potential, and 8 gives a reason for the observed but unexplained Regge trajectory like J M 2 behavior seen in quark composite particle spin families.
Quark-lepton complementarity revisited
Zhang, Xinyi; Ma, Bo-Qiang
2012-01-01
We reexamine the quark-lepton complementarity (QLC) in nine angle-phase parametrizations with the latest result for a large lepton mixing angle $\\vartheta_{13}$ from the T2K, MINOS and Double Chooz experiments. We find that the original form of the QLC two relations only hold in the standard parametrization (P1) and only one of the relations holds in P2, P3, P4, P5, P6 and P9 parametrizations separately. We also work out the corresponding reparametrization-invariant form of the relations and examine the resulting expressions with the data. The results can be used as check of the validity of the QLC relations, as well as new perspective into the issue of seeking the connection between quarks and leptons.
Wang, X J; Wang, Xiao-Jun; Yan, Mu-Lin
1999-01-01
We study SU(3)$_L\\timesSU(3)_R$ chiral quark model of mesons up to next leading order of $1/N_c$ expansion. Composite vector and axial-vector mesons resonances are introduced via non-linear realization of chiral SU(3) and vector meson dominant. Effects of one-loop graphs of pseudoscalar, vector and axial-vector mesons is calculated systematically and the significant results are obtained. Correction of effective gluon interaction is studied too. The light quark masses are introduced via new mechanism which agree with phenomenology and the requirement of chiral symmetry. Up to powers four of derivatives, chiral effective lagrangian of mesons is derived and evaluated to next leading order of $1/N_c$. Low energy limit of the model is examined. Ten low energy coupling constants $L_i(i=1,2,...,10)$ in ChPT are obtained and agree with ChPT well.
Walsh, Karen McNulty
2011-03-28
Near-light-speed collisions of gold ions provide a recipe for in-depth explorations of matter and fundamental forces. The Relativistic Heavy Ion Collider (RHIC) has produced the most massive antimatter nucleus ever discovered—and the first containing an anti-strange quark. The presence of strange antimatter makes this antinucleus the first to be entered below the plane of the classic Periodic Table of Elements, marking a new frontier in physics.
Search for strange quark matter
Hill, J C
2000-01-01
We present results of a search for charged and neutral strangelets produced on collisions of 11.6 A GeV/c Au beams with Pt or Pb targets. Yields of light nuclei and hypernuclei produced by coalescence were measured. Penalty factors were measured for the addition to a fragment of a nucleon or strange hadron. These are useful in planning future searches for strange quark matter.
Covariant diagrams for one-loop matching
Energy Technology Data Exchange (ETDEWEB)
Zhang, Zhengkang [Michigan Univ., Ann Arbor, MI (United States). Michigan Center for Theoretical Physics; Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2016-10-15
We present a diagrammatic formulation of recently-revived covariant functional approaches to one-loop matching from an ultraviolet (UV) theory to a low-energy effective field theory. Various terms following from a covariant derivative expansion (CDE) are represented by diagrams which, unlike conventional Feynman diagrams, involve gaugecovariant quantities and are thus dubbed ''covariant diagrams.'' The use of covariant diagrams helps organize and simplify one-loop matching calculations, which we illustrate with examples. Of particular interest is the derivation of UV model-independent universal results, which reduce matching calculations of specific UV models to applications of master formulas. We show how such derivation can be done in a more concise manner than the previous literature, and discuss how additional structures that are not directly captured by existing universal results, including mixed heavy-light loops, open covariant derivatives, and mixed statistics, can be easily accounted for.
Quark masses and their hierarchies
Ida, M.
1987-12-01
Electroweak symmetry breaking is attributed to dynamical generation of quark masses. Quarks q (and leptons l) are assumed to be produced by hypercolor confinement of preons at an intermediate scale Λ hc. Hierarchies observed in the q mass spectra can be explained by a BCS mechanism if the color interaction is enough asymptotically free and if residual ones emerging by the confinement are medium strong. The former assumption claims that N≦4, where N is the family number of q and l. Dynamical equations to determine q masses and mixings are given, but they require knowledge on the physics at Λ hc. A phenomenological approach is also made on the basis of an SU(7)× SU(7) chiral preon model with N=4. The mass ratio m t/ mb is related to ( m c/ m s)ηB with η B≃1.1 and m t'/ mb' to ( m u/ m d)ηA with η A≃1.4. In this scheme the fourth down quark is the heaviest (˜ 110 GeV) and contributes dominantly to F 2, where F is the Fermi scale.
Quark confinement mechanism for baryons
Goncharov, Yu P
2013-01-01
The confinement mechanism proposed earlier and then successfully applied to meson spectroscopy by the author is extended over baryons. For this aim the wave functions of baryons are built as tensorial products of those corresponding to the 2-body problem underlying the confinement mechanism of two quarks. This allows one to obtain the Hamiltonian of the quark interactions in a baryon and, accordingly, the possible energy spectrum of the latter. Also one may construct the electric and magnetic form factors of baryon in a natural way which entails the expressions for the root-mean-square radius and anomalous magnetic moment. To ullustrate the formalism in the given Chapter for the sake of simplicity only symmetrical baryons (i.e., composed from three quarks of the same flavours) $\\Delta^{++}$, $\\Delta^{-}$, $\\Omega^-$ are considered. For them the masses, the root-mean-square radii and anomalous magnetic moments are expressed in an explicit analytical form through the parameters of the confining SU(3)-gluonic fi...
Electrically Charged Strange Quark Stars
Negreiros, Rodrigo P; Malheiro, Manuel; Usov, Vladimir
2009-01-01
The possible existence of compact stars made of absolutely stable strange quark matter--referred to as strange stars--was pointed out by E. Witten almost a quarter of a century ago. One of the most amazing features of such objects concerns the possible existence of ultra-strong electric fields on their surfaces, which, for ordinary strange matter, is around $10^{18}$ V/cm. If strange matter forms a color superconductor, as expected for such matter, the strength of the electric field may increase to values that exceed $10^{19}$ V/cm. The energy density associated with such huge electric fields is on the same order of magnitude as the energy density of strange matter itself, which, as shown in this paper, alters the masses and radii of strange quark stars at the 15% and 5% level, respectively. Such mass increases facilitate the interpretation of massive compact stars, with masses of around $2 M_\\odot$, as strange quark stars.
Better Hadronic Top Quark Polarimetry
Tweedie, Brock
2014-01-01
Observables sensitive to top quark polarization are important for characterizing or even discovering new physics. The most powerful spin analyzer in top decay is the down-type fermion from the W, which in the case of leptonic decay allows for very clean measurements. However, in many applications it is useful to measure the polarization of hadronically decaying top quarks. Usually it is assumed that at most 50% of the spin analyzing power can be recovered in this case. This paper introduces a simple and truly optimal hadronic spin analyzer, with a power of 64% at leading-order. The improvement is demonstrated to be robust in a handful of simulated measurements, including the spins and spin correlations of boosted top quarks from multi-TeV top-antitop resonances, the spins of semi-boosted tops from chiral stop decays, and the potentially CP-violating spin correlations induced in continuum top pairs by color dipole operators. For the boosted studies, we explore jet substructure techniques that exhibit improved ...
Lattice Landau gauge quark propagator and the quark-gluon vertex
Oliveira, Orlando; Silva, Paulo J; Skullerud, Jon-Ivar; Sternbeck, Andre; Williams, Anthony G
2016-01-01
We report preliminary results of our ongoing lattice computation of the Landau gauge quark propagator and the soft gluon limit of the quark-gluon vertex with 2 flavors of dynamical O(a) improved Wilson fermions.
Vector Susceptibility of QCD Vacuum from an Effective Quark-Quark Interaction
Institute of Scientific and Technical Information of China (English)
ZONG Hong-Shi; QI Shi; CHEN Wei; WU Xiao-Hua
2003-01-01
.A new approach for calculating vacuum susceptibilities from an effective quark-quark interaction model is derived. As a special case, the vector vacuum susceptibility is calculated. A comparison with the results of the previous approaches is given.
Vector Susceptibility of QCD Vacuum from an Effective Quark-Quark Interaction
Institute of Scientific and Technical Information of China (English)
ZONGHong-Shi; QIShi; CHENWei; WUXiao-Hua
2003-01-01
A new approach for calculating vacuum susceptibilities from an effective quark-quark interaction model is derived. As a special case, the vector vacuum susceptibility is calculated. A comparison with the results of the previous approaches is given.
Effect of a Small Current Quark Mass on Dressed Gluon and Quark Propagator
Institute of Scientific and Technical Information of China (English)
HOU Feng-Yao; GU Jian-Zhong; ZONG Hong-Shi; L(U)Xiao-Fu
2004-01-01
Based on the Dyson-Schwinger approach, a method for obtaining the small current quark mass effect on the dressed gluon and quark propagator is developed. A comparison with the results of the previous approach is given.
QQqq Four-Quark Bound States in Chiral SU(3) Quark Model
Institute of Scientific and Technical Information of China (English)
ZHANG Ming; ZHANG Hai-Xia; ZHANG Zong-Ye
2008-01-01
The possibility of QQqq heavy-light four-quark bound states has been analyzed by means of the chiral SU(3) quark model, where Q is the heavy quark (c or b) and q is the light quark (u, d, or s). We obtain a bound state for the bbnn configuration with quantum number JP=1+, I=0 and for the ccnn (JP=1+, I=0) configuration, which is not bound but slightly above the D*D* threshold (n is u or d quark). Meanwhile, we also conclude that a weakly bound state in bbnn system can also be found without considering the chiral quark interactions between the two light quarks, yet its binding energy is weaker than that with the chiral quark interactions.
A New Model for Quark Mass Matrix
Institute of Scientific and Technical Information of China (English)
JIANG Zhi-Wei
2011-01-01
We study the status of S3, I.e. A slightly broken symmetry of quarks and propose a new model in which the S3 symmetry among the three generation up-quarks is slightly broken into the C2 symmetry while the S3 symmetry of the down-quarks is completely broken in a different way.%@@ We study the status of Sa, i.e.a slightly broken symmetry of quarks and propose a new model in which the Sa symmetry among the three generation up-quarks is slightly broken into the C symmetry while the S symmetry of the down-quarks is completely broken in a different way.
Physics of the nucleon sea quark distributions
Energy Technology Data Exchange (ETDEWEB)
Vogt, R.
2000-03-10
Sea quark distributions in the nucleon have naively been expected to be generated perturbatively by gluon splitting. In this case, there is no reason for the light quark and anti-quark sea distributions to be different. No asymmetries in the strange or heavy quark sea distributions are predicted in the improved parton model. However,recent experiments have called these naive expectations into question. A violation of the Gottfried sum rule has been measured in several experiments, suggesting that (bar u) < (bar d) in the proton. Additionally, other measurements, while not definitive, show that there may be an asymmetry in the strange and anti-strange quark sea distributions. These effects may require nonperturbative explanations. In this review we first discuss the perturbative aspects of the sea quark distributions. We then describe the experiments that could point to nonperturbative contributions to the nucleon sea. Current phenomenological models that could explain some of these effects are reviewed.
Single top quark production with CMS
Mitra, Soureek
2016-01-01
Measurements of single top quark production are presented, performed using CMS data collected in 2011, 2012 and 2015 at centre-of-mass energies of 7, 8 and 13 TeV respectively. The cross sections for the electroweak production of single top quarks in the t-channel and in association with W-bosons is measured and the results are used to place constraints on the CKM matrix element Vtb. In the t-channel the ratio of top and anti-top production cross sections is determined and compared with predictions from different parton density distribution functions. In the same channel, the inclusive cross-section in the fiducial volume is also measured. Measurements of top quark properties in single top quark production such as the top-quark polarisation, W-helicity in top quark decay and searches for anomalous couplings to gluons, photons are also presented,. A search for the s-channel is also performed.
Experimental Studies of Top Quark Production
Wagner-Kuhr, Jeannine
2016-01-01
In this review article three promising aspects of top quark production are discussed: the charge asymmetry in top quark pair production, the search for resonant top quark pair production, and electroweak single top quark production. First, an overview of the theoretical predictions of top quark pair and single top quark production is given. Then, for each topic the general analysis strategy and improvements are exemplarily explained using selected analyses and are put into the context of the global status at the beginning of LHC Run II and progress in this field. The example analyses discussed in more detail in this article use data from the LHC experiment CMS and for the charge asymmetry studies also data from the Tevatron experiment CDF have been used.
Using the Single Quark Transition Model to predict nucleon resonance amplitudes
Ramalho, G
2014-01-01
We present predictions for the $\\gamma^\\ast N \\to N^\\ast$ helicity amplitudes, where $N^\\ast$ is a member of the $[70,1^-]$ supermultiplet. We combine the results from the single quark transition model for the helicity amplitudes with the results of the covariant spectator quark model for the $\\gamma^\\ast N \\to N^\\ast(1535)$ and $\\gamma^\\ast N \\to N^\\ast(1520)$ transitions. The theoretical estimations from the covariant spectator quark model are used to calculate three independent functions $A,B$, and $C$ of $Q^2$, where $Q^2=-q^2$ and $q$ is the momentum transfer. With the knowledge of the functions $A,B$, and $C$ we estimate the helicity amplitudes for the transitions $\\gamma^\\ast N \\to N^\\ast(1650)$, $\\gamma^\\ast N \\to N^\\ast(1700)$, $\\gamma^\\ast N \\to \\Delta(1620)$, and $\\gamma^\\ast N \\to \\Delta(1700)$. The analysis is restricted to reactions with proton targets. The predictions for the transition amplitudes are valid for $Q^2 > 2$ GeV$^2$.
Energy Technology Data Exchange (ETDEWEB)
Barik, N.; Das, M. (Utkal Univ., Bhubaneswar (India). Dept. of Physics)
1983-01-13
Several properties of octet baryons such as (i) the magnetic moment, (ii) (Gsub(A)/Gsub(v))sub(n) for neutron ..beta..-decay and (iii) the charge radius of the proton have been calculated in a simple independent-quark model under the assumption that the individual constituent quarks are confined, in first approximation, by a relativistic power-law potential Vsub(q)(r)=(1+..beta..) (asup(..nu..+1)rsup(..nu..)+V/sub 0/) with a, ..nu..>0. In view of the simplicity of the model, the results obtained are quite encouraging.
Tevatron Top-Quark Combinations and World Top-Quark Mass Combination
Peters, Reinhild Yvonne; ATLAS, on behalf of the; CDF; CMS; collaborations, D0
2014-01-01
Almost 20 years after its discovery, the top quark is still an interesting particle, undergoing precise investigation of its properties. For many years, the Tevatron proton antiproton collider at Fermilab was the only place to study top quarks in detail, while with the recent start of the LHC proton proton collider a top quark factory has opened. An important ingredient for the full understanding of the top quark is the combination of measurements from the individual experiments. In particula...
Radiatively induced quark and lepton mass model
Nomura, Takaaki; Okada, Hiroshi
2016-10-01
We propose a radiatively induced quark and lepton mass model in the first and second generation with extra U (1) gauge symmetry and vector-like fermions. Then we analyze the allowed regions which simultaneously satisfy the FCNCs for the quark sector, LFVs including μ- e conversion, the quark mass and mixing, and the lepton mass and mixing. Also we estimate the typical value for the (g - 2) μ in our model.
Top quark mass measurements at CDF
Energy Technology Data Exchange (ETDEWEB)
Maki, Tuula; /Helsinki U. /Helsinki Inst. of Phys.
2007-10-01
The top quark mass is interesting both as a fundamental parameter of the standard model as well as an important input to precision electroweak tests. The CDF Collaboration has measured the top quark mass with high precision in all decay channels with complementary methods. A combination of the results from CDF gives a top quark mass of 170.5{+-}1.3(stat.){+-}1.8(syst.) GeV/c{sup 2}.
On quark number susceptibilities at high temperatures
Bazavov, A; Hegde, P; Karsch, F; Miao, C; Mukherjee, Swagato; Petreczky, P; Schmidt, C; Velytsky, A
2013-01-01
We calculated second and fourth order quark number susceptibilities for 2+1 flavor QCD in the high temperature region using two improved staggered fermion formulations. The calculations are performed at several lattice spacing and we show that in the continuum limit the two formulations give consistent results. We compare our continuum extrapolated results on quark number susceptibilities with recent weak coupling calculations, and find that these cannot simultaneously explain the lattice results for second and fourth order quark number susceptibilities.
Overview of top quark physics at ATLAS
Finelli, Kevin Daniel; The ATLAS collaboration
2016-01-01
Analyses of top quark pair production, single top production, and measurements of top quark properties are presented, showing the scope of recent ATLAS activities in the field. Many of these measurements test the predictions of the standard model in regimes and modes that have not previously been explored. Several top quark measurements are also being used to set limits on theories of new physics beyond the standard model, for example using an effective field theory framework.
Quark Physics without Quarks: A Review of Recent Developments in S-Matrix Theory.
Capra, Fritjof
1979-01-01
Reviews the developments in S-matrix theory over the past five years which have made it possible to derive results characteristic of quark models without any need to postulate the existence of physical quarks. In the new approach, the quark patterns emerge as a consequence of combining the general S-matrix principles with the concept of order.…
Quark Physics without Quarks: A Review of Recent Developments in S-Matrix Theory.
Capra, Fritjof
1979-01-01
Reviews the developments in S-matrix theory over the past five years which have made it possible to derive results characteristic of quark models without any need to postulate the existence of physical quarks. In the new approach, the quark patterns emerge as a consequence of combining the general S-matrix principles with the concept of order.…
Transversity of quarks in a nucleon
Indian Academy of Sciences (India)
K Bora; D K Choudhury
2003-11-01
The transversity distribution of quarks in a nucleon is one of the three fundamental distributions, that characterize nucleon’s properties in hard scattering processes at leading twist (twist 2). It measures the distribution of quark transverse spin in a nucleon polarized transverse to its (inﬁnite) momentum. It is a chiral-odd twist-two distribution function – gluons do not couple to it. Quarks in a nucleon/hadron are relativistically bound and transversity is a measure of the relativistic nature of bound quarks in a nucleon. In this work, we review some important aspects of this less familiar distribution function which has not been measured experimentally so far.
Quark masses in two-flavor QCD
Creutz, Michael
2011-01-01
Considered as a function of the quark mases, two-flavor QCD depends on three parameters, including one that is CP violating. As the masses vary to unphysical values, regions of both first- and second-order phase transitions are expected. For non-degenerate quarks, non-perturbative effects leave individual quark mass ratios with a renormalization scheme dependence. This complicates matching lattice results with perturbative schemes and clarifies the tautology with attacking the strong CP problem via a vanishing up quark mass.
Top quark measurements in the CMS experiment
Lista, Luca
2017-01-01
Experimental results on top-quark physics obtained at the CMS experiment are reported based on the data recorded at centre-of-mass energy up to 13 TeV. Inclusive and differential cross sections for both top-quark pair and single top-quark production are presented, as well as measurements of top-quark properties in production and decay, and searches for anomalous couplings. The presented measurements test theoretical predictions, including recent perturbative QCD calculations, provide constraints of fundamental standard model parameters, and set limits on physics beyond the standard model.
Is Heavy Quark Axion Necessarily Hadronic Axion?
Chang, Sanghyeon; Kim, Jihn E.
1993-01-01
We show that heavy quark axion is not necessarily a hadronic axion, which manifests in the quark and lepton seesaw mechanism. We introduce a heavy $SU(2)$ singlet fermion for each known fermion in order to unify the axion scale and the seesaw scale. The light quarks and leptons gain their masses by the seesaw mechanism. Even though our axion model gives a kind of heavy quark axion, the axion has tree level lepton--axion coupling suppressed by $F_a$, contrary to a widely known belief that heav...
CP Violation in Single Top Quark Production
Energy Technology Data Exchange (ETDEWEB)
Geng, Weigang [Michigan State Univ., East Lansing, MI (United States)
2012-01-01
We present a search for CP violation in single top quark production with the DØ experiment at the Tevatron proton-antiproton collider. CP violation in the top electroweak interaction results in different single top quark production cross sections for top and antitop quarks. We perform the search in the single top quark final state using 5.4 fb^{-1} of data, in the s-channel, t-channel, and for both combined. At this time, we do not see an observable CP asymmetry.
Measurements and searches with top quarks
Energy Technology Data Exchange (ETDEWEB)
Peters, Reinhild Yvonne [Univ. of Wuppertal (Germany)
2008-08-01
In 1995 the last missing member of the known families of quarks, the top quark, was discovered by the CDF and D0 experiments at the Tevatron, a proton-antiproton collider at Fermilab near Chicago. Until today, the Tevatron is the only place where top quarks can be produced. The determination of top quark production and properties is crucial to understand the Standard Model of particle physics and beyond. The most striking property of the top quark is its mass--of the order of the mass of a gold atom and close to the electroweak scale--making the top quark not only interesting in itself but also as a window to new physics. Due to the high mass, much higher than of any other known fermion, it is expected that the top quark plays an important role in electroweak symmetry breaking, which is the most prominent candidate to explain the mass of particles. In the Standard Model, electroweak symmetry breaking is induced by one Higgs field, producing one additional physical particle, the Higgs boson. Although various searches have been performed, for example at the Large Electron Positron Collider (LEP), no evidence for the Higgs boson could yet be found in any experiment. At the Tevatron, multiple searches for the last missing particle of the Standard Model are ongoing with ever higher statistics and improved analysis techniques. The exclusion or verification of the Higgs boson can only be achieved by combining many techniques and many final states and production mechanisms. As part of this thesis, the search for Higgs bosons produced in association with a top quark pair (t$\\bar{t}$H) has been performed. This channel is especially interesting for the understanding of the coupling between Higgs and the top quark. Even though the Standard Model Higgs boson is an attractive candidate, there is no reason to believe that the electroweak symmetry breaking is induced by only one Higgs field. In many models more than one Higgs boson are expected to exist, opening even more
Thermal Recombination: Beyond the Valence Quark Approximation
Müller, B; Bass, S A
2005-01-01
Quark counting rules derived from recombination models agree well with data on hadron production at intermediate transverse momenta in relativistic heavy-ion collisions. They convey a simple picture of hadrons consisting only of valence quarks. We discuss the inclusion of higher Fock states that add sea quarks and gluons to the hadron structure. We show that, when recombination occurs from a thermal medium, hadron spectra remain unaffected by the inclusion of higher Fock states. However, the quark number scaling for elliptic flow is somewhat affected. We discuss the implications for our understanding of data from the Relativistic Heavy Ion Collider.
Top Quark Mass Measurements at the Tevatron
Energy Technology Data Exchange (ETDEWEB)
Peters, Reinhild Yvonne [DESY
2014-01-01
Since the discovery of the top quark in 1995 by the CDF and D0 collaborations at the Fermilab Tevatron proton antiproton collider, precise measurements of its mass are ongoing. Using data recorded by the D0 and CDF experiment, corresponding to up to the full Tevatron data sample, top quark mass measurements performed in different final states using various extraction techniques are presented in this article. The recent Tevatron top quark mass combination yields m_t=173.20 +-0.87 GeV. Furthermore, measurements of the top antitop quark mass difference from the Tevatron are discussed.
Hydrodynamics of anisotropic quark and gluon fluids
Florkowski, Wojciech; Maj, Radoslaw; Ryblewski, Radoslaw; Strickland, Michael
2013-03-01
The recently developed framework of anisotropic hydrodynamics is generalized to describe the dynamics of coupled quark and gluon fluids. The quark and gluon components of the fluids are characterized by different dynamical anisotropy parameters. The dynamical equations describing such mixtures are derived from kinetic theory, with the collisional kernel treated in the relaxation-time approximation, allowing for different relaxation times for quarks and gluons. Baryon number conservation is enforced in the quark and antiquark components of the fluid, but overall parton number nonconservation is allowed in the system. The resulting equations are solved numerically in the (0+1)-dimensional boost-invariant case at zero and finite baryon density.
Hydrodynamics of anisotropic quark and gluon fluids
Florkowski, Wojciech; Ryblewski, Radoslaw; Strickland, Michael
2012-01-01
The recently developed framework of anisotropic hydrodynamics is generalized to describe the dynamics of coupled quark and gluon fluids. The quark and gluon components of the fluids are characterized by different dynamical anisotropy parameters. The dynamical equations describing such mixtures are derived from kinetic theory with the collisional kernel treated in the relaxation-time approximation. Baryon number conservation is enforced in the quark and anti-quark components of the fluid, but overall parton number non-conservation is allowed in the system. The resulting equations are solved numerically in the (0+1)-dimensional boost-invariant case at zero and finite baryon density.
Pseudoscalar meson physics with four dynamical quarks
Bazavov, A; Bouchard, C; DeTar, C; Du, D; El-Khadra, A X; Foley, J; Freeland, E D; Gamiz, E; Gottlieb, Steven; Heller, U M; Hetrick, J E; Kim, J; Kronfeld, A S; Laiho, J; Levkova, L; Lightman, M; Mackenzie, P B; Neil, E T; Oktay, M; Simone, J N; Sugar, R L; Toussaint, D; Van de Water, R S; Zhou, R
2012-01-01
We present preliminary results for light, strange and charmed pseudoscalar meson physics from simulations using four flavors of dynamical quarks with the highly improved staggered quark (HISQ) action. These simulations include lattice spacings ranging from 0.15 to 0.06 fm, and sea-quark masses both above and at their physical value. The major results are charm meson decay constants f_D, f_{D_s} and f_{D_s}/f_D and ratios of quark masses. This talk will focus on our procedures for finding the decay constants on each ensemble, the continuum extrapolation, and estimates of systematic error.
The Body Center Cubic Quark Lattice Model
Lin Xu, Jiao
2004-01-01
The Standard Model while successful in many ways is incomplete; many questions remain. The origin of quark masses and hadronization of quarks are awaiting an answer. From the Dirac sea concept, we infer that two kinds of elementary quarks (u(0) and d(0)) constitute a body center cubic (BCC) quark lattice with a lattice constant a < $10^{-18}$m in the vacuum. Using energy band theory and the BCC quark lattice, we can deduce the rest masses and the intrinsic quantum numbers (I, S, C, b and Q) of quarks. With the quark spectrum, we deduce a baryon spectrum. The theoretical spectrum is in agreement well with the experimental results. Not only will this paper provide a physical basis for the Quark Model, but also it will open a door to study the more fundamental nature at distance scales <$10^{-18}$m. This paper predicts some new quarks $u_{c}$(6490) and d$_{b}$(9950), and new baryons $\\Lambda_{c}^{+}$(6500), $\\Lambda_{b}^{0}$(9960).
Relativistic quark model and pentaquark spectroscopy
Gerasyuta, S M
2002-01-01
The relativistic five-quark equations are found in the framework of the dispersion relation technique. The solutions of these equations using the method based on the extraction of leading singularities of the amplitudes are obtained. The five-quark amplitudes for the low-lying pentaquarks are calculated under the condition that flavor SU(3) symmetry holds. The poles of five-quark amplitudes determine the masses of the lowest pentaquarks. The mass spectra of pentaquarks which contain only light quarks are calculated. The calculation of pentaquark amplitudes estimates the contributions of three subamplitudes. The main contributions to the pentaquark amplitude are determined by the subamplitudes, which include the meson states.
Single top quark production with CMS
Directory of Open Access Journals (Sweden)
Piccolo Davide
2013-11-01
Full Text Available Measurements of single top quark production performed using the CMS experiment [1] data collected in 2011 at centre-of-mass energies of 7 TeV and in 2012 at 8 TeV, are presented. The cross sections for the electroweak production of single top quarks in the t-channel and in association with W-bosons is measured and the results are used to place constraints on the CKM matrix element Vtb. Measurements of top quark properties in single top quark production are also presented. The results include the measurement of the charge ratio in the single top t-channel.
Review of meson spectroscopy: quark states and glueballs
Energy Technology Data Exchange (ETDEWEB)
Chanowitz, M.S.
1981-11-01
A group of three lectures on hadron spectroscopy are presented. Topics covered include: light L = 0 mesons, light L = 1 mesons, antiquark antiquark quark quark exotics, a catalogue of higher quark antiquark excitations, heavy quarkonium, and glueballs. (GHT)
The covariate-adjusted frequency plot.
Holling, Heinz; Böhning, Walailuck; Böhning, Dankmar; Formann, Anton K
2016-04-01
Count data arise in numerous fields of interest. Analysis of these data frequently require distributional assumptions. Although the graphical display of a fitted model is straightforward in the univariate scenario, this becomes more complex if covariate information needs to be included into the model. Stratification is one way to proceed, but has its limitations if the covariate has many levels or the number of covariates is large. The article suggests a marginal method which works even in the case that all possible covariate combinations are different (i.e. no covariate combination occurs more than once). For each covariate combination the fitted model value is computed and then summed over the entire data set. The technique is quite general and works with all count distributional models as well as with all forms of covariate modelling. The article provides illustrations of the method for various situations and also shows that the proposed estimator as well as the empirical count frequency are consistent with respect to the same parameter.
A Lorentz covariant approach to the bound state problem
Micu, L
2000-01-01
The relativistic equivalent of the Schr\\"odinger equation for a two particle bound state having the total angular momentum $S$ is written in the form of a Lorentz covariant set of equations (p_1^mu+p_2^mu+Omega^mu)Psi(p_1,p_2;P) chi_S(\\vec{p}_1,\\vec{p}_2)=P^mu Psi(p_1,p_2;P) chi_S(\\vec{p}_1,\\vec{p}_2) where the operators Omega^mu are the components of a 4-vector quasipotential. The solution of this set is a stationary function representing the distribution of spins and internal momenta in a reference frame where the momentum of the bound system is P^\\mu. The contribution of the operators Omega^mu to the bound state momentum is assumed to be the 4-momentum of a vacuum-like effective field entering the bound system as an independent component. It is shown that a state made of free quarks and of the effective field has definite mass and can be normalized like a single particle state. The generalization to the case of three or more particles is immediate.
Worldline construction of a covariant chiral kinetic theory
Mueller, Niklas; Venugopalan, Raju
2017-07-01
We discuss a novel worldline framework for computations of the chiral magnetic effect (CME) in ultrarelativistic heavy-ion collisions. Starting from the fermion determinant in the QCD effective action, we show explicitly how its real part can be expressed as a supersymmetric worldline action of spinning, colored, Grassmannian particles in background fields. Restricting ourselves for simplicity to spinning particles, we demonstrate how their constrained Hamiltonian dynamics arises for both massless and massive particles. In a semiclassical limit, this gives rise to the covariant generalization of the Bargmann-Michel-Telegdi equation; the derivation of the corresponding Wong equations for colored particles is straightforward. In a previous paper [N. Mueller and R. Venugopalan, arXiv:1701.03331.], we outlined how Berry's phase arises in a nonrelativistic adiabatic limit for massive particles. We extend the discussion here to systems with a finite chemical potential. We discuss a path integral formulation of the relative phase in the fermion determinant that places it on the same footing as the real part. We construct the corresponding anomalous worldline axial-vector current and show in detail how the chiral anomaly appears. Our work provides a systematic framework for a relativistic kinetic theory of chiral fermions in the fluctuating topological backgrounds that generate the CME in a deconfined quark-gluon plasma. We outline some further applications of this framework in many-body systems.
Highlights of top quark properties measurements at ATLAS
Barranco Navarro, Laura; The ATLAS collaboration
2017-01-01
The top quark is the heaviest known fundamental particle. As it is the only quark that decays before it hadronizes, this gives the unique opportunity to probe the properties of bare quarks. This talk will focus on a few recent precision measurements of top quark properties in production and decay by the ATLAS Collaboration. Measurements of the top quark mass and searches for rare top quark decays are also presented.
Highlights of top quark properties measurements at ATLAS
Barranco Navarro, Laura; The ATLAS collaboration
2017-01-01
The top quark is the heaviest known fundamental particle. As it is the only quark that decays before it hadronizes, this gives the unique opportunity to probe the properties of bare quarks. This talk focuses on a few recent precision measurements of top quark properties in production and decay by the ATLAS Collaboration. Measurements of the top quark mass and searches for rare top quark decays are also presented.
A covariant model for the negative parity resonances of the nucleon
Ramalho, G
2015-01-01
We present a model for the $\\gamma^\\ast N \\to N^\\ast$ helicity amplitudes, where $N$ is the nucleon and $N^\\ast$ is a negative parity nucleon excitation, member of the $SU(6)$-multiplet $[70,1^-]$. The model combines the results from the single quark transition model for the helicity amplitudes with the results of the covariant spectator quark model for the $\\gamma^\\ast N \\to N^\\ast(1535)$ and $\\gamma^\\ast N \\to N^\\ast(1520)$ transitions. With the knowledge of the amplitudes $A_{1/2}$ and $A_{3/2}$ for those transitions we calculate three independent coefficients defined by the single quark transition model and make predictions for the helicity amplitudes associated with the $\\gamma^\\ast N \\to N^\\ast(1650)$, $\\gamma^\\ast N \\to N^\\ast(1700)$, $\\gamma^\\ast N \\to \\Delta(1620)$, and $\\gamma^\\ast N \\to \\Delta(1700)$ transitions. In order to facilitate the comparison with future experimental data at high $Q^2$, we provide also simple parametrizations for the amplitudes, compatible with the expected falloff at high ...
Forecasting Covariance Matrices: A Mixed Frequency Approach
DEFF Research Database (Denmark)
Halbleib, Roxana; Voev, Valeri
This paper proposes a new method for forecasting covariance matrices of financial returns. The model mixes volatility forecasts from a dynamic model of daily realized volatilities estimated with high-frequency data with correlation forecasts based on daily data. This new approach allows...... for flexible dependence patterns for volatilities and correlations, and can be applied to covariance matrices of large dimensions. The separate modeling of volatility and correlation forecasts considerably reduces the estimation and measurement error implied by the joint estimation and modeling of covariance...... matrix dynamics. Our empirical results show that the new mixing approach provides superior forecasts compared to multivariate volatility specifications using single sources of information....
Estimation of Low-Rank Covariance Function
Koltchinskii, Vladimir; Lounici, Karim; Tsybakov, Alexander B.
2015-01-01
We consider the problem of estimating a low rank covariance function $K(t,u)$ of a Gaussian process $S(t), t\\in [0,1]$ based on $n$ i.i.d. copies of $S$ observed in a white noise. We suggest a new estimation procedure adapting simultaneously to the low rank structure and the smoothness of the covariance function. The new procedure is based on nuclear norm penalization and exhibits superior performances as compared to the sample covariance function by a polynomial factor in the sample size $n$...
Nonperturbative equation of state of quark-gluon plasma. Applications
Komarov, E V
2007-01-01
The vacuum-driven nonperturbative factors $L_i$ for quark and gluon Green's functions are shown to define the nonperturbative dynamics of QGP in the leading approximation. EoS obtained recently in the framework of this approach is compared in detail with known lattice data for $\\mu=0$ including $P/T^4$, $\\epsilon/T^4$, $\\frac{\\epsilon-3P}{T^4}$. The basic role in the dynamics at $T\\la 3T_c$ is played by the factors $L_i$ which are approximately equal to the modulus of Polyakov line for quark $L_{fund}$ and gluon $L_{adj}$. The properties of $L_i$ are derived from field correlators and compared to lattice data, in particular the Casimir scaling property $L_{adj} =(L_{fund})^{\\frac{C_2(adj)}{C_2(fund)}}$ follows in the Gaussian approximation valid for small vacuum correlation lengths. Resulting curves for $P/T^4$, $\\epsilon/T^4$, $\\frac{\\epsilon-3P}{T^4}$ are in a reasonable agreement with lattice data, the remaining difference points out to an effective attraction among QGP constituents.
Energy Technology Data Exchange (ETDEWEB)
Hinzmann, Andreas Dominik
2011-10-07
The Large Hadron Collider (LHC) at the Conseil Europeen pour la Recherche Nucleaire (CERN) allows to study the interactions of quarks and gluons in a yet unexplored energy regime. In 2010, the LHC delivered an integrated luminosity of more than 36 pb{sup -1} of proton-proton collisions at a center-of-mass energy of {radical}(s)=7 TeV. In these proton-proton collisions, the interactions of the constituent quarks and gluons produced a considerable amount of jets of particles with transverse momenta above 1 TeV. Well suited for the study of these jet processes is the Compact Muon Solenoid (CMS) experiment situated at the LHC point 5 as it can measure jets with the necessary energy and angular resolutions over a large range of transverse momentum ({proportional_to}30 GeV
quarks (quark compositeness). Models describing quarks as bound states of constituent particles may be able to explain the number of quark generations, quark masses and charges. A common signature of these models are additional contact interactions between quarks in high-momentum-transfer interactions, observable in the cross section of jet processes. Inspired by the Rutherford experiment, the scattering angle of two-jet processes (dijets) is measured to study the point-like quark and gluon scattering processes predicted by QCD. The dijet scattering angle is expressed in terms of {chi}{sub dijet} = e {sup vertical} {sup stroke} {sup y{sub 1}-y
Nucleation rate of the quark-gluon plasma droplet at ﬁnite quark chemical potential
Indian Academy of Sciences (India)
D S Gosain; S Somorendro Singh; Agam K Jha
2012-05-01
The nucleation rate of quark-gluon plasma (QGP) droplet is computed at ﬁnite quark chemical potential. In the course of computing the nucleation rate, the ﬁnite size effects of the QGP droplet are taken into account. We consider the phenomenological ﬂow parameter of quarks and gluons, which is dependent on quark chemical potential and we calculate the nucleation rate of the QGP droplet with this parameter. While calculating the nucleation rate, we ﬁnd that for low values of quark phenomenological parameter $ q$, nucleation rate is negligible and when increases, nucleation rate increases signiﬁcantly.
Quark distribution functions in the chiral quark-soliton model cancellation of quantum anomalies
Göke, K; Polyakov, M V; Schweitzer, P; Urbano, D
2001-01-01
In the framework of the chiral quark-soliton model of the nucleon we investigate the properties of the polarized quark distribution. In particular we analyse the so called anomalous difference between the representations of the quark distribution functions in terms of occupied and non-occupied quark states. By an explicit analytical calculation it is shown that this anomaly is absent in the polarized isoscalar distribution \\Delta u + \\Delta d, which is ultaviolet finite. In the case of the polarized isovector quark distribution which is also needed for the regularization of the ultraviolet divergence.
Dvornikov, Maxim
2016-12-01
We study the generation of strong large scale magnetic fields in dense quark matter. The magnetic field growth is owing to the magnetic field instability driven by the electroweak interaction of quarks. We discuss the situation when the chiral symmetry is unbroken in the degenerate quark matter. In this case we predict the amplification of the seed magnetic field 1012G to the strengths (1014 -1015)G. In our analysis we use the typical parameters of the quark matter in the core of a hybrid star or in a quark star. We also discuss the application of the obtained results to describe the magnetic fields generation in magnetars.
PREFACE: Quark Matter 2006 Conference Quark Matter 2006 Conference
Ma, Yu-Gang; Wang, En-Ke; Cai, Xu; Huang, Huan-Zhong; Wang, Xin-Nian; Zhu, Zhi-Yuan
2007-07-01
The Quark Matter 2006 conference was held on 14-20 November 2006 at the Shanghai Science Hall of the Shanghai Association of Sciences and Technology in Shanghai, China. It was the 19th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions. The conference was organized jointly by SINAP (Shanghai Institute of Applied Physics, Chinese Academy of Sciences (CAS)) and CCNU (Central China Normal University, Wuhan). Over 600 scientists from 32 countries in five continents attended the conference. This is the first time that China has hosted such a premier conference in the field of relativistic heavy-ion collisions, an important event for the Chinese high energy nuclear physics community. About one half of the conference participants are junior scientists—a clear indication of the vigor and momentum for this field, in search of the fundamental nature of the nuclear matter at extreme conditions. Professor T D Lee, honorary chair of the conference and one of the founders of the quark matter research, delivered an opening address with his profound and philosophical remarks on the recent discovery of the nature of strongly-interacting quark-gluon-plasma (sQGP). Professor Hongjie Xu, director of SINAP, gave a welcome address to all participants on behalf of the two hosting institutions. Dr Peiwen Ji, deputy director of the Mathematics and Physics Division of the Natural Science Foundation of China (NSFC), also addressed the conference participants and congratulated them on the opening of the conference. Professor Mianheng Jiang, vice president of the Chinese Academy of Sciences (CAS), gave a concise introduction about the CAS as the premier research institution in China. He highlighted continued efforts at CAS to foster international collaborations between China and other nations. The Quark Matter 2006 conference is an example of such a successful collaboration between high energy nuclear physicists in China and other nations all over the world. The
Electromagnetic Properties of S11 States in a Light Cone Quark Model
Institute of Scientific and Technical Information of China (English)
HE Jun; DONG Yu-Bing
2006-01-01
Using relativistic spin-flavor wave functions of a Lorentz-covariant light cone quark model, we calculate the electromagnetic form factors of two S11 resonances, N(1535) and N(1650), and the helicity amplitudes A1/2 and S1/2 for electroexcitation of the S11 resonances from the nucleon. The electromagnetic form factors of these S11 resonances are found to be similar to those of the nucleon in shape, while the charge form factor of neutral N(1650) is nearly zero. The relative peak height of the S11 charge form factors is controlled by the mixing angle common to both resonance wave functions. As in most quark models, there is a systematic overestimate of A1/2p in both N(1535) and N(1650) cases at the photon point. A sizeable S1/2 for all cases is produced as suggested by experiments.
Two-loop renormalization of the effective field theory of a static quark
Broadhurst, D J
1991-01-01
We give a recurrence relation for two-loop integrals encountered in the effective field theory of an infinitely heavy quark, Q, interacting with gluons and Nl massless quarks, q, from which we obtain exact two-loop results, in any dimension and covariant gauge, for the propagator of Q and the vertex function of the heavy-light current J = Q Gamma q, at zero q momentum. The anomalous dimension of the Q field agrees with the recent result of Broadhurst, Gray and Schilcher. The anomalous dimension of the current is gamma_J = d log Z_J / d log mu = - alpha_s/pi (1 + (127 + 56 zeta(2) - 10 Nl)/72) alpha_s/pi + O(alpha_s^2)) which gives the new two-loop correction to the result of Voloshin and Shifman.
Relationship between quark-antiquark potential and quark-antiquark free energy in hadronic matter
Institute of Scientific and Technical Information of China (English)
SHEN Zhen-Yu; XU Xiao-Ming
2015-01-01
In high-temperature quark-gluon plasma and its subsequent hadronic matter created in a high-energy nucleus-nucleus collision,the quark-antiquark potential depends on the temperature.The temperature-dependent potential is expected to be derived from the free energy obtained in lattice gauge theory calculations.This requires one to study the relationship between the quark-antiquark potential and the quark-antiquark free energy.When the system's temperature is above the critical temperature,the potential of a heavy quark and a heavy antiquark almost equals the free energy,but the potential of a light quark and a light antiquark,of a heavy quark and a light antiquark and of a light quark and a heavy antiquark is substantially larger than the free energy.When the system's temperature is below the critical temperature,the quark-antiquark free energy can be taken as the quark-antiquark potential.This allows one to apply the quark-antiquark free energy to study hadron properties and hadron-hadron reactions in hadronic matter.
Covariance NMR spectroscopy by singular value decomposition.
Trbovic, Nikola; Smirnov, Serge; Zhang, Fengli; Brüschweiler, Rafael
2004-12-01
Covariance NMR is demonstrated for homonuclear 2D NMR data collected using the hypercomplex and TPPI methods. Absorption mode 2D spectra are obtained by application of the square-root operation to the covariance matrices. The resulting spectra closely resemble the 2D Fourier transformation spectra, except that they are fully symmetric with the spectral resolution along both dimensions determined by the favorable resolution achievable along omega2. An efficient method is introduced for the calculation of the square root of the covariance spectrum by applying a singular value decomposition (SVD) directly to the mixed time-frequency domain data matrix. Applications are shown for 2D NOESY and 2QF-COSY data sets and computational benchmarks are given for data matrix dimensions typically encountered in practice. The SVD implementation makes covariance NMR amenable to routine applications.
Earth Observing System Covariance Realism Updates
Ojeda Romero, Juan A.; Miguel, Fred
2017-01-01
This presentation will be given at the International Earth Science Constellation Mission Operations Working Group meetings June 13-15, 2017 to discuss the Earth Observing System Covariance Realism updates.
Covariant Quantization with Extended BRST Symmetry
Geyer, B; Lavrov, P M
1999-01-01
A short rewiev of covariant quantization methods based on BRST-antiBRST symmetry is given. In particular problems of correct definition of Sp(2) symmetric quantization scheme known as triplectic quantization are considered.
Conformally covariant parametrizations for relativistic initial data
Delay, Erwann
2017-01-01
We revisit the Lichnerowicz-York method, and an alternative method of York, in order to obtain some conformally covariant systems. This type of parametrization is certainly more natural for non constant mean curvature initial data.
Hamieh, Salah; Letessier, Jean; Rafelski, Johann
2000-01-01
Lattice-QCD results provide an opportunity to model, and extrapolate to finite baryon density, the properties of the quark-gluon plasma (QGP). Upon fixing the scale of the thermal coupling constant and vacuum energy to the lattice data, the properties of resulting QGP equations of state (EoS) are developed. We show that the physical properties of the dense matter fireball formed in heavy ion collision experiments at CERN-SPS are well described by the QGP-EoS we presented. We also estimate the...
Charm physics with HISQ quarks
Davies, C T H; Kendall, I; McNeile, C; Lepage, G P; Allison, I; Woloshyn, R; Dalgic, E; Trottier, H; Follana, E; Horgan, R; Hornbostel, K; Shigemitsu, J
2008-01-01
We present an update of results from the HPQCD collaboration on charm physics using the Highly Improved Staggered Quark action. This includes a precise determination of m_c using moments of current-current correlators combined with high-order continuum QCD perturbation theory. We also include an update on the determination of alpha_s from lattice QCD, preliminary results on the determination of m_b and a summary plot of the status of the gold-plated meson spectrum. There is an appendix on tackling systematic errors in fitting using the Bayesian approach.
Color Screening and Quark-Quark Interactions in Finite Temperature QCD
Döring, M; Kaczmarek, O; Karsch, F
2007-01-01
We analyze the screening of static diquark sources in 2-flavor QCD and compare results with the screening of static quark-antiquark pairs. We show that a two quark system in a fixed color representations is screened at short distances like a single quark source in the same color representation whereas at large distances the two quarks are screened independently. At high temperatures we observe that the relative strength of the interaction in diquark and quark-antiquark systems, respectively, obeys Casimir scaling. We use this result to examine the possible existence of heavy quark-quark bound states in the high temperature phase of QCD. We find support for the existence of $bb$ states up to about $2T_c$ while $cc$ states are unlikely to be formed above $T_c$.
Tevatron Top-Quark Combinations and World Top-Quark Mass Combination
Energy Technology Data Exchange (ETDEWEB)
Peters, Reinhild Yvonne [DESY
2014-11-04
Almost 20 years after its discovery, the top quark is still an interesting particle, undergoing precise investigation of its properties. For many years, the Tevatron proton antiproton collider at Fermilab was the only place to study top quarks in detail, while with the recent start of the LHC proton proton collider a top quark factory has opened. An important ingredient for the full understanding of the top quark is the combination of measurements from the individual experiments. In particular, the Tevaton combinations of single top-quark cross sections, the ttbar production cross section, the W helicity in top-quark decays as well as the Tevatron and the world combination of the top-quark mass are discussed.
Hierarchical matrix approximation of large covariance matrices
Litvinenko, Alexander
2015-01-07
We approximate large non-structured covariance matrices in the H-matrix format with a log-linear computational cost and storage O(n log n). We compute inverse, Cholesky decomposition and determinant in H-format. As an example we consider the class of Matern covariance functions, which are very popular in spatial statistics, geostatistics, machine learning and image analysis. Applications are: kriging and optimal design
Hierarchical matrix approximation of large covariance matrices
Litvinenko, Alexander
2015-01-05
We approximate large non-structured covariance matrices in the H-matrix format with a log-linear computational cost and storage O(nlogn). We compute inverse, Cholesky decomposition and determinant in H-format. As an example we consider the class of Matern covariance functions, which are very popular in spatial statistics, geostatistics, machine learning and image analysis. Applications are: kriging and op- timal design.
Covariate analysis of bivariate survival data
Energy Technology Data Exchange (ETDEWEB)
Bennett, L.E.
1992-01-01
The methods developed are used to analyze the effects of covariates on bivariate survival data when censoring and ties are present. The proposed method provides models for bivariate survival data that include differential covariate effects and censored observations. The proposed models are based on an extension of the univariate Buckley-James estimators which replace censored data points by their expected values, conditional on the censoring time and the covariates. For the bivariate situation, it is necessary to determine the expectation of the failure times for one component conditional on the failure or censoring time of the other component. Two different methods have been developed to estimate these expectations. In the semiparametric approach these expectations are determined from a modification of Burke's estimate of the bivariate empirical survival function. In the parametric approach censored data points are also replaced by their conditional expected values where the expected values are determined from a specified parametric distribution. The model estimation will be based on the revised data set, comprised of uncensored components and expected values for the censored components. The variance-covariance matrix for the estimated covariate parameters has also been derived for both the semiparametric and parametric methods. Data from the Demographic and Health Survey was analyzed by these methods. The two outcome variables are post-partum amenorrhea and breastfeeding; education and parity were used as the covariates. Both the covariate parameter estimates and the variance-covariance estimates for the semiparametric and parametric models will be compared. In addition, a multivariate test statistic was used in the semiparametric model to examine contrasts. The significance of the statistic was determined from a bootstrap distribution of the test statistic.
Covariant action for type IIB supergravity
Sen, Ashoke
2016-07-01
Taking clues from the recent construction of the covariant action for type II and heterotic string field theories, we construct a manifestly Lorentz covariant action for type IIB supergravity, and discuss its gauge fixing maintaining manifest Lorentz invariance. The action contains a (non-gravitating) free 4-form field besides the usual fields of type IIB supergravity. This free field, being completely decoupled from the interacting sector, has no physical consequence.
Functional CLT for sample covariance matrices
Bai, Zhidong; Zhou, Wang; 10.3150/10-BEJ250
2010-01-01
Using Bernstein polynomial approximations, we prove the central limit theorem for linear spectral statistics of sample covariance matrices, indexed by a set of functions with continuous fourth order derivatives on an open interval including $[(1-\\sqrt{y})^2,(1+\\sqrt{y})^2]$, the support of the Mar\\u{c}enko--Pastur law. We also derive the explicit expressions for asymptotic mean and covariance functions.
On the covariance of residual lives
Directory of Open Access Journals (Sweden)
N. Unnikrishnan Nair
2007-10-01
Full Text Available Various properties of residual life such as mean, median, percentiles, variance etc have been discussed in literature on reliability and survival analysis. However a detailed study on covariance between residual lives in a two component system does not seem to have been undertaken. The present paper discusses various properties of product moment and covariance of residual lives. Relationships the product moment has with mean residual life and failure rate are studied and some characterizations are established.